When Atoms Change

When Atoms

What we KNOW…

• Atoms on the periodic table are neutral.

• Atoms are neutral because they have the same number of protons as electrons.

• protons  have a positive charge.

• neutrons  have no charge.

What we Also need to KNOW…

• The identity of an atom is determined

ONLY by the number of protons.

• For example… If I tell you there is an

atom with 3 protons… you know it’s a

Lithium atom.

What happens if the number of

neutrons change???

If an atom gains Neutrons…

1. The mass increases by 1 for every neutron added. 2. The charge remains neutral. (Neutrons don’t have a

charge.)

3. The number of protons and electrons stay the same.

If an atom loses Neutrons…

1. The mass decreases by 1 for every neutron taken away.

2. The charge remains neutral. (Neutrons don’t have a charge.)

What happens if the number of

neutrons change???

If an atom gains Neutrons…

1. The mass increases by 1 for every neutron added.

2. The charge remains neutral. (Neutrons don’t have a charge.)

3. The number of protons and electrons stay the same.

If an atom loses Neutrons…

1. The mass decreases by 1 for every neutron taken away.

2. The charge remains neutral. (Neutrons don’t have a charge.)

The atom is now called an

ISOTOPE!

ISOTOPE EXAMPLE

Hydrogen Atom

Has a mass of 1 and an atomic number of 1

Hydrogen Isotope

Has a mass of 2 and an atomic

ISOTOPE NOTATION

We communicate that we have an

isotope by using the Atomic Symbol of

the isotope followed by the “NEW”

mass number.

ISOTOPE NOTATION

Li-6

Ex: An Isotope of Lithium is:

Isotope INVENTORY

Completing a particle inventory for an

Isotope is almost the same as the

neutral atom EXCEPT we USE THE

“NEW” MASS NUMBER

to calculate

neutrons.

Ex: Li-6

3p+ (since it’s Lithium!!!)

Isotope Practice

• Ca

atom has a mass of

40

.

• The isotopes for Ca are:

• Ca-42, Ca-43,Ca-44, Ca-46, & Ca-48.

• 1.) How many neutrons are in a

Ca atom

and each of its

isotopes

?

2.) What are the differences and

Isotope Practice

Ca atom has a mass of 40. (atomic # =20)

The isotopes for Ca have masses of 42,43,44,46, & 48.

1.) How many neutrons are in a Ca atom and each of its isotopes?

(Ca ATOM: 40 – 20 = 20n)

(ISOTOPES: 42-20=22n, 43-20=23n, 44-20=24n, 46-20=26n, 48-20=28n)

2.) What are the differences and similarities between the Ca atom and its isotopes?

Similarities Differences

(All have 20 p+ all have 20 e- all neutral

all are Calcium)

• Everyone gets 7 blue, 7 striped, 7 clear

• Black = Protons

• Red = Neutrons

• White = Electrons

• Play 1-5 pieces per turn.

Number of neutrons and protons

Number of protons and electrons

Subtract the two to find the number of neutrons

Everyday Uses of Isotopes

What most consumers don't know is that many of these units contain a small amount of

americium-241. By utilizing the radioactive

properties of this material, smoke from a fire

can be detected at a very early stage. This early warning capability has saved many lives. In fact, studies have shown that 80% of fire injuries and 80% of fire fatalities occur in homes without

Carbon-14 Dating

Recalling that all biologic organisms contain a given concentration of carbon-14, we can use this

information to help solve questions about when the organism died. When an organism dies it has a specific ratio by mass of carbon-14 to carbon-12 incorporated in the cells of it's body. At the moment

of death, no new carbon-14 containing molecules are metabolized, therefore the ratio is at a maximum. After death, the carbon-14 to carbon-12 ratio

begins to decrease because carbon-14 is decaying

away at a constant and predictable rate.

Food Irradiation

Food irradiated by exposing it to the gamma rays of a radioisotope -- one that is widely used is

cobalt-60.

The gamma rays pass through the food to destroy many disease-causing bacteria as well as those that cause food to spoil. It’s not strong enough to

change the quality, flavor or texture of the food. The food never comes in contact with the

Reviewing Isotopes

What are isotopes gaining or losing?

Here is an Atom of Oxygen (how many neutrons?) Atomic Mass=16

These are isotopes of Oxygen O-17 O-18

So…How many neutrons does each isotope of Oxygen NOW have?

8 neutrons

Neutrons!

Isotope Practice

1.)How many neutrons are in each of Zinc’s

isotopes?

Zn-65

Zn-64

____

Zn-67

_____

Zn-70

____

2.) What are the differences and

Isotope Practice

1.)How many neutrons are in each of Zinc’s isotopes? Zn-65

Zn-64____ Zn-67_____ Zn-70____

2.) What are the differences and similarities between the Zn atom and its isotopes?

34

37

40

Similarities Differences

• _{All have 30 p+ all have 30 e-} • all neutral

• _{all are Zinc}

Isotope Practice

1.)How many neutrons are in each of

Strontium’s

isotopes?

Sr-84____ Sr-86_____ Sr-87____

Answers:

Sr-84

46

Sr-86

48

Quiz Quick

Isotopes gain or lose…

When an atom gains neutrons,

its charge changes.

When an atom gains neutrons, the number

of protons and electrons do not change.

The only subatomic particles

that never change are…

A. Valance electrons

B. Protons

What happens if the number of

electrons change???

If an atom gains electrons…

1. The charge becomes negative. (There are more negative e- than positive p+ now!)

2. The mass stays the same (electron’s mass = 0).

3. The number of protons and neutrons stays the same.

If an atom loses electrons…

1. The charge becomes positive. (There are less negative e- than positive p+ now!)

2. The mass stays the same (electron’s mass =0).

What happens if the number of

electrons change???

If an atom gains electrons…

1. The charge becomes negative. (There are more negative e- than positive p+ now!)

2. The mass stays the same (electron’s mass = 0).

3. The number of protons and neutrons stays the same.

If an atom loses electrons…

1. The charge becomes positive. (There are less negative e- than positive p+ now!)

2. The mass stays the same (electron’s mass =0).

The atom is now called

an

ION

!!!

When atoms gain or lose electrons!

*Ions are charged particles!

Ions form so that unstable atoms can

bond with other unstable elements to

Charged Ions

Anion (-) Negatively charged ion.

Quick Quiz

If an atom loses electrons, its

mass changes?

Ions gain or lose…

Gaining electrons causes atoms to…

ION EXAMPLE

H+ is a positive hydrogen

ION

H: Is the neutral hydrogen

atom

H- : is a negative hydrogen

Ion Worksheet Answers

Li +1

Br -1

Mg +2

B+3

F -1

N -3

Cl -1

K +1

Ba +2

Te -2

Sn -4

As -3

Si +/-4

O -2

Ion Worksheet Coloring

Li +1 Br -1

Mg +2

B+3

F -1

N -3

Cl -1

K +1

Ba +2

Te -2

Sn -4

As -3

Si +/-4

O -2

What patterns did you notice from

coloring your ions on the periodic table?

*hint* there is more than one!

• The families were the same color.

• The families had the same ionic charge.

• Metals have a positive charge.

• Non-metals have a negative charge.

• Metals lose electrons.

Practice

Draw the Bohr models for the

following elements and find the ionic charges for each.

How is the neutral

atom

Se

and it’s isotope

Se-78

similar and

different?

(Set up a “T” chart) Similar

Same element Same # of protons Same # of electrons

Same charges

Different

Different masses

How are isotopes and ions similar and

different?

(hint* think about particles, masses and charges)

Similarities

Same number of

protons only!

Differences

Diff Masses

Diff Number of

neutrons

Diff Charges

Diff Number of

Practice

Draw the Bohr models for the

following elements and find the ionic charges for each.

Patterns on

the

+1

+2 +3 +/-4 -3 -2 -1

0

1 Shell 3 Shells 4 Shells 5 Shells 6 Shells 7 Shells 2 Shells Period 1 Period 2 Period 4 Period 3 Period 5 Period 6 Period 7

Families/Groups have a lot

in common

…

• We now know that elements in a group all

have the same # of valence e-.

• We also now know they all form ions with

the same charge.

• But…there are a lot of other properties

that elements in a family also share!

Atomic Radius (Width

)

• Atomic radius is simply the radius (width) of the atom, an indication of the atom's volume.

• Periods - atomic radius decreases as you go from

left to right across a period.

• Why?

• Stronger attractive forces in atoms (as you go

from left to right) between the opposite charges in the nucleus and electron cloud cause the atom to be 'sucked' together a little tighter.

Atomic Radius (Width)

• Groups - atomic radius increases as you

go down a group.

• Why?

• There is a significant jump in the size of

the nucleus (protons + neutrons) each

time you move from period to period

down a group. Additionally, new energy

levels of electron clouds are added to

the atom as you move from period to

period down a group, making the each

Ionization Energy

required to remove the outermost electron. It is closely related to electronegativity.

• Group - ionization energy decreases as you go

down a group.

• Why?

• The shielding effect makes it easier to

Electronegativity

• Electronegativity is an atom's 'desire' to grab another atom's electrons.

• Period - electronegativity increases as you go from left to right across a period.

• Why?

• Elements on the left of the period table have 1 -2 valence electrons and would rather give those few valence electrons away, as a result, they

have low electronegativity.

Electronegativity

• Electronegativity is an atom's 'desire' to grab another atom's electrons.

• Group - electronegativity decreases as you go down a group.

• Why?

• Elements near the top of the period table have few electrons to begin with; every electron is a big deal. They have a stronger desire to acquire more electrons. Elements near the bottom of the chart have so many electrons that loosing or

Reactivity

• Elements become more reactive as you go

down a group on the left side

• And more reactive as you go up a group on

the right side!

• Reactivity refers to how likely or vigorously an atom is to react with other substances.

• Based on this, where are the most reactive elements found on the periodic table?

What are (7) things you can now predict

about the element

Iodine (I)

, based on

where it is located on the Periodic Table?

1. It has 7 valence electrons

2. It has 5 energy rings/shells

3. It is a non-metal

4. It’s gaining 1 electron

5. It’s ionic charge is -1

6. Less reactive than Br and Cl

Properties of Non-metals

• No luster

• Brittle

• Not ductile

• Not malleable

(dull)

What can you now tell me about the

element

Nitrogen (N)

and

Potassium (K)

,

based on where they are located on the

Periodic Table?

(think about shells, valence e’s, charges, metal/non-metal, gaining/losing e’s)

Potassium

• 1 valence electron • It has 4 energy rings • It is a metal

• It’s losing 1 electron • It’s ionic charge is +1

Nitrogen

•5 valence electrons

•_{It has 2 energy rings}

•It is a non-metal

•It’s gaining 3 electrons

You are the bus driver. At your first

stop, you pick up 29 people. On your

second stop, 18 of those 29 people get

off, and at the same time 10 new

passengers arrive. At your next stop, 3

of those 10 passengers get off, and 13

new passengers come on. On your fourth

stop 4 of the remaining 10 passengers

get off, 6 of those new 13 passengers

get off as well, then 17 new passengers

get on. What is the color of the bus