Unit 2 Atomic Structure

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Unit 2 – Atomic Structure

Big Idea: Atomic structure explains patterns in the behavior of elements and allows us to predict the chemical

and physical behavior of a given element. The organization of elements on the periodic table reflects trends in

both atomic structure and element properties.

Lesson 1

Pre-Assessment activity: What does an atom look like?

Lab: Law of Definite Proportions (Mg + Cu(C

2

H

3

O

2

)

2

→ Cu + Mg(C

2

H

3

O

2

)

2

)

Lesson 2

Group activity: Model of the atom – Take 1: Create an atomic model using lab data

Law of Definite Proportions

Dalton’s Atomic Theory

Lesson 3

Thomson and Cathode Rays

Model of the Atom – Take 2

Rutherford and Gold Foil

Model of the Atom – Take 3

Lesson 4

Hydrogen Emission Spectrum

Electron Energy and Light

Model of the Atom – Take 4

Lesson 5

Electromagnetic Spectrum

Energy, Frequency, Wavelength

Flame Test Lab

Lesson 6

Build an Atom PhET simulation – protons, neutrons, electrons

Lesson 7

Isotopes and Atomic Mass PhET simulation

Lesson 8

Calculating Average Atomic Mass – Beaninum lab

Lesson 9

Electron Configurations

Model of the Atom – Take 5

Lesson 10

Cracking the Periodic Table code

Electron Configuration Practice

Lesson 11

Patterns in Valence Electrons

Ions

Lesson 12

Patterns on the Perioidic Table – Mendeleev’s ideas

Lesson 13

Coulombic Attraction POGIL activity

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Names___________________________________Period_________

Trish Loeblein 8/18/12 (I am unsure of the origin of this lab. I have made many changes – my appreciation to the unknown original author)

CHEMISTRY LAB BEANIUM – Isotope Analogy

Learning goals: Students will

explore the concept of isotopes and average atomic mass using an analogy

use their ideas in other situations

Directions:

Obtain a sample of beanium atoms from stock container. Sort the beanium atoms into

three groups, each group representing a different isotope. In the observation section,

sketch a picture of each beanium isotope to distinguish between each isotope. Fill out the

Recording and Calculations section using appropriate units.

Recording Data and Calculations:

A. Initial observations:

Number of type one Beaniums (isotope-1)

_____

Number of type two Beaniums (isotope-2)

_____

Number of type three Beaniums

(isotope-3)

_____

B. Calculate the total number of beans_____ Sample calculation here:_______________

C. Calculate the percentage of each type of isotope.

Percentage of Beanium-1 _____ sample calculation here:_______________ Percentage of Beanium-2 _____

Percentage of Beanium-3 _____

D. Calculate the average mass of each isotope.

Total mass of type one Beans_____Average mass of Beanium-1 ____ Sample calculation here: _______________ Total mass of type two Beans ___ Average mass of Beanium-2 _____ Total mass of type three Beans___ Average mass of Beanium-3 _____

Application of isotope type problems

1. 140 students participated in a knowledge retrieval session. 25 scored 90 out of 100; 63 scored 80 out of 100; 31 scored 70 out of 100; 15 scored 60 out of 100; 6 scored 50 on the knowledge retrieval session. Determine the average score on this knowledge retrieval session. Show all work.

2. Magnesium consists of three isotopes with masses of 23.98 (78.6%), 24.98 (10.1%), and 25.98 (11.3%). Calculate the average atomic mass of Mg. Show all work.

3. Copper consists of two isotopes, one with a mass of 62.96 and 70.5% abundant. The other isotope has a mass of 64.96. Determine the atomic mass of Cu. Show all work.

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BUILD AN ATOM 1

TITLE Build an Atom AUTHORS

Timothy Herzog (Weber State University) Emily Moore (University of Colorado Boulder) COURSE

General Chemistry I TYPE

In-Class Guided-Inquiry Activity TEACHING MODE

Facilitated Group Inquiry LEARNING GOALS Students will be able to:

 Use information about the number of protons, neutrons, and electrons to: o Identify an element and its position on the periodic table.

o Determine whether an atom is neutral or an ion.

o Predict the charge and determine the mass of an atom or ion.

 Relate the number of protons, neutrons and electrons to representations, including atomic symbols and the symbols found on the periodic table.

 Explain: element symbol, charge, atomic number, mass number, and isotope.

COPYRIGHT

This work is licensed under a Creative Commons Attribution 4.0 International License. This license allows users to share and adapt the materials, as long as appropriate attribution is given (with a link to the original), an indication if changes have been made, and an indication of the original licensing.

(5)

BUILD AN ATOM 2

BUILD AN ATOM

PART I: ATOM SCREEN

Build an Atom simulation (http://phet.colorado.edu/en/simulation/build-an-atom) 1. Explore the Build an Atom simulation with your group. As you explore, talk about what you

find. 2.

a) List two things your group observed in the simulation. b) What particle(s) are found in the center of the atom?

3. Play until you discover which particle(s) determine(s) the name of the element you build. What did you discover?

4. What is the name of the following atoms?

a) An atom with 3 protons and 4 neutrons: _____________ b) An atom with 2 protons and 4 neutrons: _____________ c) An atom with 4 protons and 4 neutrons: _____________

5. Play with the simulation to discover which particles affect the charge of an atom or ion. a) Fill in the blanks below to show your results:

Neutral atoms have the same number of protons and electrons. Positive ions have ________________________________ protons than electrons. Negative ions have _______________________________ protons than electrons.

b) Develop a relationship (in the form of a single sentence or equation) that can predict the charge based on the number and types of particle.

6. Play with the simulation to discover what affects the mass number of your atom or ion. a) What is a rule for determining the mass number of an atom or ion?

7. Practice applying your understanding by playing 1st and 2nd levels on the game screen.

Commented [TH1]:

This style of question encourages students to complete a full exploration of the sim and to articulate their findings, without needing the teacher to give instructions for each interaction. The teacher could ask students to share out their list with the class.

Minimal (or no) instructor introduction is required before students begin the activity and sim exploration.

Commented [TH2]: After a significant portion of the class

has completed the first page, or once many of them are engaged with the Game, a class discussion around Part I is suggested.

In the class discussion, focus particular attention on students’ answers to questions 5(b) and 6, which allow for a greater diversity of student thinking.

(6)

BUILD AN ATOM 3

PART II: SYMBOL SCREEN

8. Using the Symbol readout box, figure out which particles affect each component of the atomic symbol.

a) In the atomic symbol below, label each letter (a, b, c, and d) with: the particle(s) used to determine the letter, and

how the value of each letter is determined.

9. Create a definition (using a complete sentence) for each of these items based on your labels from the atomic symbol above.

a) Element Symbol b) Charge

c) Atomic Number d) Mass Number

10. Practice applying your understanding by playing the 3rd and 4th game levels. Play until you can get all the questions correct on the 4th level.

11. In addition to atomic symbol, we can represent atoms by name and mass number. a) Complete the table below:

Symbol Name

Carbon-12

b) Each representation (Symbol and Name) in the table above provides information about the atom. Describe the similarities and differences between the Symbol and Name representations.

c

d

a

b

6 12

C

+1 5 11

B

9 18

F

Commented [TH3]: Part II focuses primarily on student

understanding and use of symbolic representations, specifically isotopic symbols.

A facilitated discussion at the end of this section is advised, particularly if students share-out their definitions from question 9 and compare representations as a class.

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BUILD AN ATOM 4

PART III: ISOTOPES

12. Play with the simulation to determine:

a) Which particles affect the stability of the atom? _____________________ b) Which particles do not affect the stability of the atom? _______________ 13. What are the names of the stable forms of oxygen?

a) Oxygen-16 b) Oxygen-____ c) Oxygen-____

d) List all of the things that are the same about these atoms (ignore the electrons).

e) List all of the things that are different about these atoms (ignore the electrons).

14. The atoms in the previous question are isotopes of each other. Based on this information, list the requirements for two atoms to be isotopes of each other.

15. Test your understanding of isotopes by examining the relationships between the pairs of atoms listed below:

Atom 1 Atom 2 Relationship between atom 1 and atom 2

Isotopes

Same Atom, Not Isotopes of Each Other Different Element

Carbon-12

Isotopes

Same Atom, Not Isotopes of Each Other Different Element

Argon-40 Argon-41

Isotopes

Same Atom, Not Isotopes of Each Other Different Element

Boron-10

Isotopes

Same Atom, Not Isotopes of Each Other Different Element An atom with 13 protons and 13 neutrons An atom with 14 protons and 13 neutrons Isotopes

Same Atom, Not Isotopes of Each Other Different Element 6 12

C

6 13

C

6 12

C

5 11

B

Commented [YC4]: Part III of the activity extends the use

of the sim representations to enable students to construct a definition of isotopes.

(8)

BUILD AN ATOM 5

EXERCISES

16. The periodic table has a great deal of information about every atom. Using your periodic table, answer the following questions:

a) What is the atomic number of chlorine (Cl)? _____ b) What is the atomic number of tungsten (W)? _____ c) How many protons are there in any Cl atom?_____ d) How many protons are there in any Te atom? _____

e) Can you tell from the periodic table exactly how many neutrons are in an atom? 17. Complete the following table:

Name Symbol Atomic number Mass Number Number of neutrons Number of Electrons Charge hydrogen-2 2H 1 2 1 1 0 3H sodium-22 22Na+ 10 12 24 12 12 25 13 46Ti-2 107Ag 19F-1 carbon-12 6 carbon-13 6 carbon-14 6 carbon-12 7 carbon-12 5 4He 8 8 10 argon-40 18 18 70Ga 70Ga+3 4 9 2 7 8 8

18. To test your knowledge of isotopes, draw arrows between all pairs of atoms in the table above that are isotopes of each other.

Commented [TH5]: The exercises on this page may be best

left as a homework assignment, as it is difficult to complete this in addition to the rest of the activity during class. Additionally, this section extends to elements outside of the scope of the simulation.

(9)

BUILD AN ATOM

1

BUILD AN ATOM

PART I: ATOM SCREEN

Build an Atom simulation (

http://phet.colorado.edu/en/simulation/build-an-atom

)

1. Explore the Build an Atom simulation with your group. As you explore, talk about what you

find.

2.

a) List two things your group observed in the simulation.

b) What particle(s) are found in the center of the atom?

3. Play until you discover which particle(s) determine(s) the name of the element you build.

What did you discover?

4. What is the name of the following atoms?

a) An atom with 3 protons and 4 neutrons: _____________

b) An atom with 2 protons and 4 neutrons: _____________

c) An atom with 4 protons and 4 neutrons: _____________

5. Play with the simulation to discover which particles affect the charge of an atom or ion.

a) Fill in the blanks below to show your results:

Neutral atoms have the same number of protons and electrons.

Positive ions have ________________________________ protons than electrons.

Negative ions have _______________________________ protons than electrons.

b) Develop a relationship (in the form of a single sentence or equation) that can predict the

charge based on the number and types of particle.

6. Play with the simulation to discover what affects the mass number of your atom or ion.

a) What is a rule for determining the mass number of an atom or ion?

(10)

BUILD AN ATOM

2

PART II: SYMBOL SCREEN

8.

Using the Symbol readout box, figure out which particles affect each component of the atomic

symbol.

a) In the atomic symbol below, label each letter (a, b, c, and d) with:

the particle(s) used to determine the letter, and

how the value of each letter is determined.

9. Create a definition (using a complete sentence) for each of these items based on your labels

from the atomic symbol above.

a) Element Symbol

b) Charge

c) Atomic Number

d) Mass Number

10. Practice applying your understanding by playing the 3

rd

and 4

th

game levels. Play until you

can get all the questions correct on the 4

th

level.

11. In addition to atomic symbol, we can represent atoms by name and mass number.

a) Complete the table below:

Symbol

Name

Carbon-12

b) Each representation (Symbol and Name) in the table above provides information about

the atom. Describe the similarities and differences between the Symbol and Name

representations.

c

d

a

b

6

12

C

+

1

5

11

B

9 18

F

(11)

BUILD AN ATOM

3

PART III: ISOTOPES

12. Play with the simulation to determine:

a) Which particles affect the stability of the atom? _____________________

b) Which particles do not affect the stability of the atom? _______________

13. What are the names of the stable forms of oxygen?

a) Oxygen-16

b) Oxygen-____

c) Oxygen-____

d) List all of the things that are the same about these atoms (ignore the electrons).

e) List all of the things that are different about these atoms (ignore the electrons).

14. The atoms in the previous question are isotopes of each other. Based on this information, list

the requirements for two atoms to be isotopes of each other.

15. Test your understanding of isotopes by examining the relationships between the pairs of

atoms listed below:

Atom 1

Atom 2

Relationship between atom 1 and atom 2

Isotopes

Same Atom, Not Isotopes of Each Other

Different Element

Carbon-12

Isotopes

Same Atom, Not Isotopes of Each Other

Different Element

Argon-40

Argon-41

Isotopes

Same Atom, Not Isotopes of Each Other

Different Element

Boron-10

Isotopes

Same Atom, Not Isotopes of Each Other

Different Element

An atom with 13

protons and 13

neutrons

An atom with 14

protons and 13

neutrons

Isotopes

Same Atom, Not Isotopes of Each Other

Different Element

6

12

C

6

13

C

6

12

C

5

11

B

(12)

BUILD AN ATOM

4

EXERCISES

16. The periodic table has a great deal of information about every atom. Using your periodic

table, answer the following questions:

a) What is the atomic number of chlorine (Cl)? _____

b) What is the atomic number of tungsten (W)? _____

c) How many protons are there in any Cl atom?_____

d) How many protons are there in any Te atom? _____

e) Can you tell from the periodic table exactly how many neutrons are in an atom?

17. Complete the following table:

Name

Symbol

Atomic

number

Mass

Number

Number of

neutrons

Number of

Electrons

Charge

hydrogen-2

2

H

1

2

1

1

0

3

H

sodium-22

22

Na

+

10

12

24

12

12

25

13

46

Ti

-2 107

Ag

19

F

-1

carbon-12

6

carbon-13

6

carbon-14

6

carbon-12

7

carbon-12

5

4

He

8

8

10

argon-40

18

18

70

Ga

70

Ga

+3

4

9

2

7

8

8

18. To test your knowledge of isotopes, draw arrows between all pairs of atoms in the table above

that are isotopes of each other.

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Clicker Questions for

Build an Atom

AUTHORS:

Yuen-ying Carpenter (University of Colorado Boulder)

Trish Loeblein (University of Colorado Boulder)

Robert Parson (University of Colorado Boulder)

COURSE:

Introductory / Preparatory College Chemistry

COPYRIGHT: This work is licensed under a

Creative Commons Attribution 4.0 International

License

.

(14)

If you have 5 protons and 6 neutrons,

how many electrons would you add to

make a neutral atom ?

a. 5 electrons

b. 6 electrons

c. 11 electrons

(15)

If you have an atom with

8 protons, 9 neutrons and 10 electrons,

what is its mass number?

a. Zero

b. 8

c. 16

d. 17

e. 25

?

(16)

a. Neutral atom

b. +2 ion

c. +1 ion

d. -1 ion

e. -2 ion

For the same atom, with

8 protons, 9 neutrons and 10 electrons,

what type of atom or ion is it?

(17)

If you have 5 protons,

6 neutrons, & 5 electrons,

what would the symbol

look like?

(18)

Start atom

Final atom

Remove

Which statement is FALSE about the final atom?

a.

It is a different element than the start

atom.

b.

It has 4 neutrons less than the start atom.

c.

It has 2 protons less than the start atom.

(19)

What is the correct symbol for an isotope of

carbon with 7 neutrons?

a.

6

C

b.

7

C

c.

13

C

d.

13

6

C

6

13

7

(20)

What is the correct identity of an element with the

following isotopic symbol and how many neutrons

does it have?

a. Gold, 114 neutrons

b. Bromine, 44 neutrons

c. Gold, 44 neutrons

d. Bromine, 114 neutrons

X

79

35

(21)

Which are isotopes?

I

II

III

a. I and II

b. II and III

c.

I and III

d. I, II and III

(22)

Which of these pairs of atoms are isotopes?

Pair A

Pair B

Pair C

# of protons

6

8

5

2

12

12

(23)

Which of these is

not

an isotope of

?

6

14

C

a.

An atom with 6 protons and 7 neutrons.

b.

The atom

c.

An atom with 8 protons and 6 neutrons.

d.

The ion

6

12

C

6

(24)

Suppose you built a scale model of the atom

the same width as a football field (100 m).

What could you use to represent the nucleus in

your model?

A. A marble (1 cm)

B. A golf ball (4 cm)

C. A soccer ball (20 cm)

(25)

Clicker Questions for

Isotopes and Atomic Mass

AUTHORS:

Yuen-ying Carpenter (University of Colorado Boulder)

Robert Parson (University of Colorado Boulder)

Trish Loeblein (University of Colorado Boulder)

COURSE:

Introductory Chemistry

COPYRIGHT: This work is licensed under a

Creative Commons Attribution 4.0 International

License

.

(26)

What would this be?

a. Carbon-12

b. Carbon-14

c. Oxygen-14

d. More than

one of these

(27)

Reason:

The number of protons tells the name

of the atom; the mass is given by the

sum of protons and neutrons

(28)

Which of these pairs of atoms are isotopes?

Pair A

Pair B

Pair C

# of protons

6

8

5

2

12

12

(29)

What is the approximate average mass of a

hydrogen atom in this sample?

a. 6 amu

b. 2 amu

c. 1.5 amu

d. 1 amu

(30)

3/6 gives 50% of each, so…

0.5*2 + 0.5*1 = 1.5 amu

or

3*2 + 2*1 = 1.5 amu

Why are there more digits in the answer in the sim?

(31)

What is the approximate

average mass of an argon

atom in this sample?

(32)

Calculation:

(33)

Is the average atomic mass closer to the mass of a lithium-6 atom

or a lithium-7 atom?

a. Lithium-6

b. Lithium-7

6.41548

Mass of 1 atom

= 7.01600 amu

Mass of 1 atom

= 6.01512 amu

(34)

To figure this out, let’s start with some small samples…

Will the average atomic mass of sample 2 be…

a.

More than Sample 1

b.

Same as Sample 1

c.

Less than Sample 1

d.

I don’t know how to determine this.

?

6.41548

Mass of 1 atom

= 7.01600 amu

Mass of 1 atom

= 6.01512 amu

(35)

Sample 2

Equal to Sample 1

6.41548 amu average

Equal to Sample 1

(36)

In nature, chlorine has the following composition:

The average atomic mass of a natural sample of chlorine is…

About

36 amu

b

Between

36-37 amu

c

Between

35-36 amu

a

(37)

Neon has three naturally occurring isotopes:

20

Ne 19.992 amu

21

Ne 20.994 amu

22

Ne 21.991 amu

Which isotope has the highest natural abundance?

a.

20

Ne

b.

21

Ne

c.

22

Ne

d. All isotopes have the same abundance

e. Impossible to tell from this information

10

Ne

(38)

Magnesium has three naturally occurring isotopes:

24

Mg

23.985 amu

25

Mg 24.986 amu

26

Mg 25.983 amu

In a sample with an average atomic mass of 24.98 amu,

which isotope is the most abundant?

a.

24

Mg

b.

25

Mg

c.

26

Mg

d.

All isotopes have the same abundance

e.

Impossible to tell from this information

(39)

Neon has three naturally occurring isotopes:

20

Ne

21

Ne

22

Ne

Which isotope has the highest natural abundance?

Can we answer the question without being given the exact

isotopic masses?

a.

Yes

b.

No

10

Ne

20.18

(40)

Neon has three naturally occurring isotopes:

20

Ne

21

Ne

22

Ne

Which isotope has the highest abundance in a sample of Ne?

Can we answer the question without being given the average

atomic mass of the sample?

a.

Yes

b.

No

(41)

Neon has three naturally occurring isotopes:

20

Ne

21

Ne

22

Ne

Which isotope has the highest abundance in a sample of Ne

with average atomic mass of _________?

Can we answer the question for any sample, no matter what the

average atomic mass?

a.

Yes

b.

No

(42)

Argon has three stable isotopes, with these atomic masses:

36

Ar

35.968 amu

38

Ar

37.963 amu

40

Ar

39.962 amu

You measure the average atomic mass of several different

samples of argon, and are asked to predict the most abundant

isotope in each sample.

For which of these samples is this prediction impossible?

Sample A, a naturally-occurring sample of argon

Sample B, average atomic mass = 36.5 amu

Sample C, average atomic mass = 37.5 amu

Sample D, average atomic mass = 39.5 amu

(43)

Complete the following sentence with a

unit.

On average, lithium weighs 6.941 ____.

a. g / atom

b. g / mol

c. amu / mol

d. amu / atom

e. More than one of the above

Lithium

3

Li

(44)

ISOTOPES AND ATMOIC MASS 1

TITLE

Isotopes and Atomic Mass AUTHORS

Timothy Herzog (Weber State University) COURSE

General Chemistry I TYPE

In-Class Guided-Inquiry Activity TEACHING MODE

Facilitated Group Inquiry LEARNING GOALS Students will be able to:

 Explain the difference between atomic mass and mass number

 Calculate average atomic mass from percent abundance and isotopic mass. COPYRIGHT

This work is licensed under a Creative Commons Attribution 4.0 International License. This license allows users to share and adapt the materials, as long as appropriate attribution is given (with a link to the original), an indication if changes have been made, and an indication of the original licensing.

(45)

ISOTOPES AND ATOMIC MASS 2

ISOTOPES AND ATOMIC MASS MODEL 1: Make Isotopes

Open the Isotopes and Atomic Mass simulation

http://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass

Play with the “Make Isotopes” tab of the simulation for a few minutes and then answer the following questions.

1. What particles determine the mass number? 2. Why is mass number always a whole number?

3. One isotope of carbon (C) has exactly the same mass number and atomic mass since it was used as the definition of the atomic mass unit (amu). Which isotope is it and what is its atomic mass?

4. What is the approximate mass of one proton? __________amu 5. What is the approximate mass of one neutron? __________amu

6. Look at 3 or 4 other atoms using the simulation. Do any of them have a whole number for atomic mass?

MODEL 2: Mix Isotopes

Play with the “Mix Isotopes” tab for a few minutes, then answer the following questions. 1. What are the factors that affect the average atomic mass of a mixture of isotopes?

2. Beryllium (Be) and Fluorine (F) have only one stable isotope. Use the sim and the periodic table to complete the following table:

Element Mass of 1 atom Average mass of 2 atoms (sim) Average mass of 3 atoms (sim) Atomic mass (periodic table) Beryllium (Be) 9.01218 amu Fluorine (F) 18.99840 amu

3. Why are all the values in each row of the table above the same?

Commented [YC1]: Learning goals:

 Explain the difference between atomic mass and mass number

 Calculate average atomic mass from percent abundance and isotopic mass.

Commented [TH2]: Facilitation tip:

This is a good time to stop and briefly discuss mass defect and possible E=mc2 and to reinforce the reasons why 12C

(46)

ISOTOPES AND ATOMIC MASS 3 4. Lithium has only two stable isotopes. Use the sim to determine the following:

a. Atomic mass of lithium-6 = __________________amu b. Atomic mass of lithium-7 = __________________amu

c. Average atomic mass of a sample containing three lithium-6 atoms and two lithium-7 atoms. ______________amu

d. Is the average atomic mass you just determined closer to the mass of lithium-6 or lithium-7? Explain

5. Describe a method to calculate the average atomic mass of the sample in the previous question using only the atomic masses of lithium-6 and lithium-7 without using the simulation.

6. Test your method by creating a few sample mixtures of isotopes with the sim and see if your method correctly predicts the average atomic mass of that sample from only the atomic masses of the isotopes and the quantity of each isotope. Use the table below to track your progress.

Element Atomic mass and quantity of each isotope

Average atomic mass of sample (calculate yourself)

Average atomic mass of sample (from simulation)

MODEL 3: Nature’s mix of isotopes

1. Using the sim, examine “Nature’s mix of isotopes” for several different elements. If you assumed 100 total atoms in a sample, how could you relate the % values shown in the sim into a number you could use for your calculation of average atomic mass?

Commented [YC3]: Facilitation tip:

Questions 5-6 in this section focus on the calculation of average atomic mass using the number of atoms of each isotope, which is typically easier for students than the calculation of average atomic mass from percent abundance. We extend this calculation to the use of percent abundances in the next section, Nature’s Mix of Isotopes

(47)

ISOTOPES AND ATOMIC MASS 4 2. Calculate the atomic mass of each of the following elements using your method from above.

Test your answer using the Nature’s mix of isotopes and the periodic table. Keep going until you can get two in a row right.

Isotope 1 Isotope 2 Isotope 3 Check answer with sim

Element (amu) Mass %age (amu) Mass %age (amu) Mass %age

Calculated average atomic mass (amu) Yes No Hydrogen 1.007 99.98 2.01410 0.011 - - Silicon 27.97 92.22 28.9764 4.685 29.97377 3.092 Nitrogen 14.00 99.63 15.0001 0.364 - - Argon 35.96 0.336 37.9627 0.063 39.96238 99.60 Calculations / Rough work:

(48)

ISOTOPES AND ATOMIC MASS 5

EXERCISES

1. Titanium has five common isotopes: 46Ti (8.00%), mass= 45.953 amu 47 Ti (7.80%), mass= 46.952 amu 48Ti (73.40%), mass= 47.947 amu 49Ti (5.50%), mass= 48.948 amu 50Ti (5.30%), mass = 49.945 amu

Calculate the average atomic mass of titanium.

2. The atomic mass of boron is 10.81 amu. Boron has two isotopes: Boron-10 has a mass of 10.01 amu. Boron-11 has a mass of 11.01 amu. What is the %age of each isotope in boron? (check your answer with the simulation)

3. A certain sample of rubidium has just two isotopes, 85Rb (mass = 84.911amu) and 87Rb (mass = 86.909amu). The atomic mass of this sample is 86.231 amu. What are the percentages of the isotopes in this sample?

Commented [TH4]: These exercises could be left for

take-home practice, as they focus primarily on computational skill, not conceptual understanding.

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ISOTOPES AND ATMOIC MASS

1

ISOTOPES AND ATOMIC MASS

MODEL 1:

Make Isotopes

Open the Isotopes and Atomic Mass simulation

http://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass

Play with the “Make Isotopes” tab of the simulation for a few minutes and then answer the

following questions.

1. What particles determine the mass number?

2. Why is mass number always a whole number?

3. One isotope of carbon (C) has exactly the same mass number and atomic mass since it was

used as the definition of the atomic mass unit (amu). Which isotope is it and what is its

atomic mass?

4. What is the approximate mass of one proton? __________amu

5. What is the approximate mass of one neutron? __________amu

6. Look at 3 or 4 other atoms using the simulation. Do any of them have a whole number for

atomic mass?

MODEL 2:

Mix Isotopes

Play with the “Mix Isotopes” tab for a few minutes, then answer the following questions.

1. What are the factors that affect the average atomic mass of a mixture of isotopes?

2. Beryllium (Be) and Fluorine (F) have only one stable isotope. Use the sim and the periodic

table to complete the following table:

Element

Mass of 1 atom

Average mass of 2

atoms (sim)

Average mass of 3

atoms (sim)

Atomic mass

(periodic table)

Beryllium

(Be)

9.01218 amu

Fluorine

(F)

18.99840 amu

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ISOTOPES AND ATOMIC MASS

2

4. Lithium has only two stable isotopes. Use the sim to determine the following:

a. Atomic mass of lithium-6 = __________________amu

b. Atomic mass of lithium-7 = __________________amu

c. Average atomic mass of a sample containing three lithium-6 atoms and two lithium-7

atoms. ______________amu

d. Is the average atomic mass you just determined closer to the mass of lithium-6 or

lithium-7? Explain

5. Describe a method to calculate the average atomic mass of the sample in the previous

question using only the atomic masses of lithium-6 and lithium-7 without using the

simulation.

6. Test your method by creating a few sample mixtures of isotopes with the sim and see if your

method correctly predicts the average atomic mass of that sample from only the atomic

masses of the isotopes and the quantity of each isotope. Use the table below to track your

progress.

Element

Atomic mass and

quantity of each isotope

Average atomic mass

of sample

(calculate yourself)

Average atomic mass of

sample (from simulation)

MODEL 3:

Nature’s mix of isotopes

1. Using the sim, examine “Nature’s mix of isotopes” for several different elements. If you

assumed 100 total atoms in a sample, how could you relate the % values shown in the sim

into a number you could use for your calculation of average atomic mass?

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ISOTOPES AND ATOMIC MASS

3

2. Calculate the atomic mass of each of the following elements using your method from above.

Test your answer using the Nature’s mix of isotopes and the periodic table. Keep going until

you can get two in a row right.

Isotope 1

Isotope 2

Isotope 3

Check answer

with sim

Element

(amu)

Mass

%age

(amu)

Mass

%age

(amu)

Mass

%age

Calculated average atomic mass (amu)

Yes

No

Hydrogen 1.007

99.98 2.01410 0.011

-

-

Silicon

27.97

92.22 28.9764 4.685

29.97377

3.092

Nitrogen

14.00

99.63 15.0001 0.364

- -

Argon

35.96

0.336 37.9627 0.063

39.96238

99.60

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ISOTOPES AND ATOMIC MASS

4

EXERCISES

1. Titanium has five common isotopes:

46

Ti (8.00%), mass= 45.953 amu

47

Ti (7.80%), mass= 46.952 amu

48

Ti (73.40%), mass= 47.947 amu

49

Ti (5.50%), mass= 48.948 amu

50

Ti (5.30%), mass = 49.945 amu

Calculate the average atomic mass of titanium.

2. The atomic mass of boron is 10.81 amu. Boron has two isotopes: Boron-10 has a mass of

10.01 amu. Boron-11 has a mass of 11.01 amu. What is the %age of each isotope in boron?

(check your answer with the simulation)

3. A certain sample of rubidium has just two isotopes,

85

Rb (mass = 84.911amu) and

87

Rb (mass = 86.909amu). The atomic mass of this sample is 86.231 amu. What are the

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1 Hanson, A.J. 2015

Unit 2 – Atomic Structure

Big Idea: Atomic structure explains patterns in the behavior of elements and allows us to predict the chemical and physical behavior of a given

element. The organization of elements on the periodic table reflects trends in both atomic structure and element properties.

Essential Questions:

1) How do we know what an atom looks like if we can’t see atoms? 2) Why are silver and gold used to make jewelry?

3) Why are chlorine and iodine used as disinfectants?

4)

Why do we use helium to inflate balloons instead of hydrogen?

Colorado Academic Standard:

SC09-GR.HS-S.1-GLE.2 Matter has definite structure that determines characteristic physical and chemical properties.

Evidence Outcomes: a) Develop, communicate, and justify an evidence-based scientific explanation supporting the current model of an atom.

b) Use characteristic physical and chemical properties to develop predictions and supporting claims about elements’ positions on the periodic table.

NGSS:

Structure and Properties of Matter

Performance Expectation: HS-PS1-1 Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.

Disciplinary Core Ideas:

PS1.A: Structure and Properties of Matter

 Each atom has a charges substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.

 The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patters of outer electron states.

PS2.B: Types of Interactions

 Attraction and repulsion between electric charges at the atomic scale explain the structure, properties, and transformations of matter, as well as the contact forces between material objects.

Science and Engineering Practices:

Developing and Using Models

 Use a model to predict the relationships between systems or between components of a system.

Crosscutting Concepts:

Patterns

 Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.

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2 Hanson, A.J. 2015

Motion and Stability: Forces and Interactions

Performance Expectation: HS-PS2-4 Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects.

Disciplinary Core Ideas:

PS2.B Types of Interactions

 Newton’s law of universal gravitation and Coulomb’s law provide the mathematical models to describe and predict the effects of gravitational and electrostatic forces between distant objects.

 Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnets or electric currents cause magnetic fields; electric charges or changing magnetic fields cause electric fields.

Science and Engineering Practices:

Using Mathematics and Computational Thinking

 Use mathematical representations of phenomena to describe explanations.

Crosscutting Concepts:

Patterns

 Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.

Waves and Electromagnetic Radiation

Performance Expectation: HS-PS4-1 Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and

speed of waves traveling in various media.

Disciplinary Core Ideas:

PS4.A: Wave Properties

 The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.

Science and Engineering Practices:

Using Mathematics and Computational Thinking

 Use mathematical representations of phenomena or design solutions to describe and/or support claims and/or explanations.

Crosscutting Concepts:

Cause and Effect

 Empirical evidence is required to differentiate between cause and correlations and make claims about specific causes and effects.

Performance Expectation: HS-PS4-3 Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other.

Disciplinary Core Ideas:

PS4.B: Electromagnetic Radiation

 Electromagnetic radiation (e.g., radio, microwaves, light) can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features.

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3 Hanson, A.J. 2015

Science and Engineering Practices:

Engaging in Argument from Evidence

 Evaluate the claims, evidence and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.

Crosscutting Concepts:

Systems and System Models

 Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions-including energy, matter, and information flows-within and between systems at different scales.

Lesson Number

In Class Activity Learning Objectives Students will be able to:

Homework

1 Question of the day: What does an atom look

like?

Activities:

 Groups draw pictures or make models to show the basic structure of an atom. Drawings/models should show location of protons, neutrons, and electrons, but do not need to be to scale.

 Law of Definite Proportions – Lab Activity – Mg (s) + Cu(C2

H

3

O

2

)

2

(aq)

 Describe what an atom looks like using background knowledge from previous science classes.

 Experimentally determine the mass ratio of Mg and Cu in a chemical reaction.

 Relate the experimentally determined mass ratio of magnesium to copper to the Law of Definite

Proportions.

Calculate the mass ratio of Mg to Cu using experimental data.

Rough draft of atomic model using evidence collected in lab activity.

2 Question of the day: What does an atom look

like?

Activities:

 Model of the Atom – Take 1 (groups use lab data ONLY to propose a model of an atom)

 Class discussion/clicker questions for about Law of Definite Proportions

 Dalton’s atomic theory

 Relate the experimentally determined mass ratio of magnesium to copper to the Law of Definite

Proportions.

 Explain the major postulates of Dalton’s atomic theory.

 Develop an atomic model based on experimental evidence obtained in class from the reaction between Mg and copper (II) acetate.

 Compare student generated models of the atom with Dalton’s atomic theory/model.

Writing assignment: Using the Law of Definite Proportions and your

experimental data, justify the atomic model you created with your group in class. Compare and contrast your model to the atomic model proposed by Dalton.

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4 Hanson, A.J. 2015

Lesson Number

In Class Activity Learning Objectives Students will be able to:

Homework

3 Question of the day: What does an atom look

like? How did we discover electrons and protons?

Activities:

 Thomson’s cathode ray experiment demonstration

Model of the Atom – Take 2

 Battleship game – modeling Rutherford’s gold foil experiment

 Rutherford scattering PhET simulation

 Model of the Atom – Take 3

 Describe J.J. Thomson’s experiment with cathode ray tubes and the evidence he collected about atomic structure.

 Analyze the billiard ball model of the atom using the results of Thomson’s cathode ray tube experiment.

 Propose an atomic model that uses Thomson’s data from the cathode ray tube experiment.

 Describe the experiment Rutherford used to test Thomson’s atomic model.

 Analyze the plum pudding model of the atom using the results of Rutherford’s gold foil experiment.

 Propose an atomic model that uses Rutherford’s data from the gold foil experiment.

 Explain the experimental evidence Rutherford used to propose the nuclear model of the atom.

 Compare and contrast the plum pudding and nuclear models of an atom.

 Compare the plum pudding and nuclear atomic models to student generated models of the atom.

Writing assignment: Compare and contrast the Billiard Ball, Plum Pudding, and Nuclear Models of the atom. Cite experimental evidence used to develop each model. State reasons the model was revised.

4 Question of the day: What does an atom look

like? Where are electrons found in an atom? What evidence do we have to support this idea?

Activities:

 View hydrogen spectrum

 Electron Energy and Light POGIL activity

 Model of the Atom – Take 4

 Describe what you see when electricity is passed through a glass tube containing hydrogen gas.

 Define “quantum” and explain what it means for energy to be quantized.

 Analyze the nuclear model of the atom using evidence from Bohr’s experiments.

 Explain where Bohr thought electrons were located in an atom.

 Describe the experimental evidence that Bohr used to develop his atomic model.

 Compare the Bohr model of the atom to student generated models of the atom.

Writing assignment:

Compare and contrast the Bohr model of the atom to previous atomic models. Cite experimental evidence used to develop each model. State reasons the model was revised.

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5 Hanson, A.J. 2015

Lesson Number

In Class Activity Learning Objectives Students will be able to:

Homework

5 Question of the day: What does an atom

look like? Where are electrons found in an atom? What evidence do we have to support this idea?

Activities:

 Energy, frequency, wavelength calculations

 Flame test lab

 Calculate the wavelength, frequency, or energy of electromagnetic radiation.

 Explain what causes different colors of light in a fireworks show.

 Describe how the emission spectrum of an element is related to its electron arrangement.

Wavelength, Energy, Frequency Practice sheet

6 Question of the day: How do we know

the number of protons, neutrons, and electrons in an atom? How can we calculate the mass number of an atom?

Activities:

Build an Atom PhET Simulation

 Describe the charge, mass, and location of protons, neutrons and electrons in an atom.

 Write and interpret atomic symbols.

 Calculate the mass number of an atom.

 Determine the number of protons, neutrons, and electrons in a neutral atom.

Complete all 4 levels of the game in Build an Atom. Screenshot your results and submit on Edmodo.

7 Question of the day: Are all atoms of the

same element identical?

Activities:

 Isotopes and Atomic Mass PhET simulation

 Define the term isotope.

 Identify atoms that represent two different isotopes of the same element.

 Describe factors that make an atom stable or unstable.

 Develop a procedure to determine the average atomic mass of an element.

Write a procedure to determine the average atomic mass of an element.

8 Question of the day:

How is atomic mass calculated?

Activities:

 Average mass of Candium or Beanium

 Calculating average atomic mass of elements

 Develop and carry out a procedure to determine the average mass of a sample of beans or candy.

 Explain the difference between an average and a weighted average.

 Write and carry out a procedure to calculate the average atomic mass of an element.

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6 Hanson, A.J. 2015

Lesson Number

In Class Activity Learning Objectives Students will be able to:

Homework

9 Question of the day: What does an atom

look like? What is incorrect about the Bohr model of the atom? What evidence do we have to support this idea?

Activities:

 View neon and argon emission spectrum.

 Models of the Hydrogen Atom PhET simulation (demonstration)

 Electron Configuration POGIL activity

 Model of the Atom – Take 5

 Describe what you see when electricity is passed through a glass tube containing neon or argon gas.

 Analyze the Bohr model of the atom using evidence from the neon and argon emission spectra.

 Propose a new atomic model to account for data that does not fit the Bohr model.

Writing assignment:

Explain why the Bohr model of the atom needed to be revised. Cite experimental evidence that was used to support the idea that Bohr’s model needed to be revised.

10 Question of the day: Why doesn’t the

periodic table list elements in alphabetical order?

Activities:

 Cracking the Periodic Table Code POGIL

 Practice electron configurations

 Write an electron configuration for any element in the first four periods on the periodic table.

 Explain how the periodic table can be used to determine the electron configuration of an atom of any element on the periodic table.

 Use the periodic table to predict where the last electrons are located in an atom of any element listed on the periodic table.

Writing assignment:

Compare and contrast the quantum mechanical model of the atom to previous atomic models. Cite experimental evidence used to develop the quantum mechanical model.

11 Question of the day: Why doesn’t the

periodic table list elements in alphabetical order?

Activities:

 Valence Electron

 Ion formation – Build an Atom PhET Simulation revisited

 Identify the valance electrons in an atom using the electron configuration.

 Relate the number of valence electrons to an element’s location on the periodic table.

 Calculate the charge, mass, and number of protons, neutrons, and electrons in an ion.

Valence Electrons and Ions Practice Sheet

12 Question of the day: How was the first

periodic table constructed? What is “periodic” about the periodic table?

Activities:

 Alien card sort

 What was Mendeleev Thinking?

 Explain how the first periodic table of the elements was created.

Reading assignment: Creating the First Periodic Table

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7 Hanson, A.J. 2015

Lesson Number

In Class Activity Learning Objectives Students will be able to:

Homework

13 Question of the day: What types of

attraction occur between the nucleus and the electrons?

Activities:

Coulombic Attraction POGIL Activity

 Explain the factors that influence the strength of the electrostatic attraction between oppositely charged particles.

Coulombic Attraction Practice sheet

14 Question of the day: What is “periodic”

about the periodic table? What patterns exist on the periodic table?

Activities:

Mini-lab: Properties of Elements

 Periodic Trends POGIL activity or Graphing Periodic Trends activity

 List the properties of metals, nonmetals, and metalloids.

 Classify an element based on its properties.

 Relate the location and atomic structure of an element to its physical properties.

 Analyze the trends in atomic radius, first ionization energy, and electronegativity on the periodic table.

 Justify the trends in atomic radius, first ionization energy, and electronegativity using your knowledge of atomic structure.

 Given a list of elements, place the elements in order of increasing or decreasing atomic radius, first ionization energy, or electronegativity. Justify your reasoning.

Writing assignment:

Periodic Trends – Atomic Radius, Ionization Energy, and Electronegativity

15 Assessments

RAFT Assignment: Choose one of the

following essential questions for this chapter to complete your RAFT assignment:

 How do we know what an atom looks like if we can’t see atoms?

 Why are silver and gold used to make jewelry?

 Why are chlorine and iodine used as disinfectants?

 Why do we use helium to inflate balloons instead of hydrogen?

RAFT assignment Study for Unit 2 test.

Figure

Updating...

References