In this section you will… Review the Model of the Atom Describe the Properties of the Proton Describe the Properties of the Neutron Describe the Properties of the Electron

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Technical Science

Introduction to Chemistry

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Elements, Isotopes, & Ions

● In this section you will…

– Review the Model of the Atom

– Describe the Properties of the Proton

– Describe the Properties of the Neutron

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Review the Model

of the Atom

● You also explored the properties of the three subatomic particles.

● Complete the following slides to summarize the structure

of the atom and the properties of the subatomic particles

● In the previous tutorial “The Atom”, you made a model of the atom.

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Review the Model

of the Atom

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● Atoms are composed of 3 subatomic particles.

Proton

Neutron

Electron

● The protons and neutrons are located in a small area in the the center of the atom called the nucleus.

Nucleus

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Review the Model

of the Atom

● Summarize the Model of the Atom

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Subatomic Particle

Mass Charge Location

? Name the three subatomic particles.

Proton

Neutron

Electron

? Record the mass of each particle.

1 AMU

0 AMU

? Record the charge of each particle.

+ 1

0

- 1

? Record the location of the particles.

Nucleus

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Review the Model

of the Atom

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● Our model of the atom is a representation of the most current information about atoms.

● It places the protons and neutrons in a small dense nucleus in the center with the electrons moving

around the outside.

● In the following sections you will explore each of the subatomic particles in more

detail and learn how each

contributes to the properties of the atom.

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Describe the Properties

of the Proton

Proton

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● There are approximately 109 different types of atoms. 88 occur naturally. 21 are man-made.

● An element is a pure substance composed entirely of one type of atom.

● Protons are the most important subatomic particle because they determine the type of atom.

Home

Subatomic

Particle Mass Charge Location

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Describe the Properties

of the Proton

Proton

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● The numbers of protons in the first 8 elements are listed below.

● The number of protons

determine the type of atom.

● In other words, if an atom has 8 protons, it must be an

oxygen atom.

● If an atom is oxygen, it must have 8 protons.

Element # Protons

Hydrogen 1

Helium 2

Lithium 3

Beryllium 4

Boron 5

Carbon 6

Nitrogen 7

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Describe the Properties

of the Proton

Proton

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● Because of the important role the protons play in determining the element …

● The number of protons in an atom is called the Atomic Number.

● Oxygen has 8 protons therefore it has an

atomic number of 8.

Element # Protons

Hydrogen 1

Helium 2

Lithium 3

Beryllium 4

Boron 5

Carbon 6

Nitrogen 7

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Describe the Properties

of the Proton

Proton

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● Complete the table below?

Element # Protons Atomic Number

Hydrogen 1

Helium 2

Lithium 3

Beryllium 4

Boron 5

Carbon 6

Nitrogen 7

Oxygen 8

1 2

3 4

5 6

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Describe the Properties

of the Proton

Proton

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● What is the only element that has atoms with 3 protons?

● How many protons will an atom of Boron always have?

Element Atomic Number

Hydrogen 1

Helium 2

Lithium 3

Beryllium 4

Boron 5

Carbon 6

Nitrogen 7

Oxygen 8

Α Lithium: A lithium atom

always has 3 protons. It has an atomic number of 3.

Α Five: It has an atomic number

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Home

Describe the Properties

of the Proton

Proton - Review

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● Protons have a mass of 1 AMU, a +1 charge, and are located in the nucleus.

● The positively charged protons make the nucleus of the atom positive as well.

● The number of protons in an atom is also called the atomic number.

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Describe the Properties

of the Neutron

Neutron

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Home

Subatomic

Neutron 1 AMU 0 Nucleus

● Neutrons, like protons, are located in the nucleus and have a mass of 1 AMU.

● Neutrons, unlike protons, have no charge.

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Describe the Properties

of the Neutron

Neutron

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● Neutrons and protons are the only particles that have mass and they are located in the nucleus.

● Therefore, the mass of an atom is determined by the number of protons and neutrons and …

● The mass is concentrated in the nucleus.

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Describe the Properties

of the Neutron

Neutron

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● Complete the table given the atomic number and the atomic mass of the atom.

Atom # Protons # Neutrons

2 Helium

4 3 Lithium

7 11 Sodium

23

Atomic Number

Atomic Mass

2 2

3 4

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Describe the Properties

of the Neutron

Neutron

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● The atomic number (# of protons) determines the type of atom (element).

● An atom with 2 protons is helium. A helium atom will always have 2 protons.

Helium

2 Protons

2 Neutrons

Atomic Number = 2

Atomic Mass = 4

☞

Elements tend to have a “usual” number of neutrons. For example, most

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Describe the Properties

of the Neutron

Neutron

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● What if two atoms have the same number of protons but a different number of neutrons?

Protons

2 2

2 1

Atomic Number = 2 Atomic Number = 2

Atomic Mass = 4 Atomic Mass = 3

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Describe the Properties

of the Neutron

Neutron

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● Since both atoms have the same atomic number they are the same element; Helium in this case.

Atomic Number = 2 _{Atomic Number = 2} Atomic Mass = 4 _{Atomic Mass = 3}

Helium Helium

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Describe the Properties

of the Neutron

Neutron

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● Atoms that have the same number of protons but a different number of neutrons are called Isotopes.

Atomic Number = 2 _{Atomic Number = 2} Atomic Mass = 4 Atomic Mass = 3

Helium Helium

● Isotopes are identified by including their mass along with their name.

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Describe the Properties

of the Neutron

Neutron

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● Although both atoms represent different forms of helium, the term isotope is usually used when

referring to the unusual form of the element.

Helium - 4 Helium - 3

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Describe the Properties

of the Neutron

Neutron

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● The table below shows some elements with their

atomic number (top) and their “usual” atomic mass.

1

Hydrogen 1

7 Nitrogen

14

8 Oxygen

16

11 Sodium

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● How many protons and neutrons are in the isotope Nitrogen-15.

Α 7 protons and 8 neutrons. If an element is nitrogen

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Describe the Properties

of the Neutron

Neutron

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1

Hydrogen 1

7 Nitrogen

14

8 Oxygen

16

11 Sodium

23

● How many protons and neutrons are in the isotope Hydrogen-3.

Α 1 proton and 2 neutrons. If an element is hydrogen

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Describe the Properties

of the Neutron

Neutron

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1

Hydrogen 1

7 Nitrogen

14

8 Oxygen

16

11 Sodium

23

● What would you call an atom with 8 protons and 9 neutrons.

Α Oxygen-17. If an atom has 8 protons, it must be

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Describe the Properties

of the Neutron

Neutron

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1

Hydrogen 1

7 Nitrogen

14

8 Oxygen

16

11 Sodium

23

● What would you call an atom with 11 protons and 11 neutrons.

Α Sodium-22. If an atom has 11 protons, it must be

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Describe the Properties

of the Neutron

Neutron - Review

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● Neutrons have a mass of 1 AMU, no charge, and are located in the nucleus.

● Neutrons along with protons determine the atomic mass of the atom.

● Two or more atoms may have the same number of protons but a different number of neutrons. This

means that they are the same element but they have a different mass.

● These different forms of the same element are called isotopes.

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Describe the Properties

of the Electron

Electron

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Home

Subatomic

Electron 0 AMU - 1 Energy Level

/ Orbitals

● Electrons are located in the energy levels and orbitals.

● Electrons have a negative one (-1) charge.

● Electrons stay in “orbit” around the nucleus because they are negatively charged and the nucleus is

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Describe the Properties

of the Electron

Electron

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● The number of electrons in an atom is equal to the number of protons before an atom reacts.

● The atomic number of an atom identifies both the number of protons and the number of electrons in an unreacted atom.

Helium

2 Protons

2 Electrons

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Element Atomic Number

# Protons

# Electrons

Hydrogen 1

Helium 2

Lithium 3

Beryllium 4

Boron 5

Carbon 6

Describe the Properties

of the Electron

Electron

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● Complete the table below.

1 1

2 2

3 3

4 4

5 ₅

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Describe the Properties

of the Electron

Electron

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● In an unreacted atom the number of protons is equal to the number of electrons. How does this

relationship effect the whole atom?

● Protons (+1) & electrons (–1) have opposite charges.

● Opposite charges not only attract but they cancel each other out. 5 positive charges can cancel out 5 negative charges. So…

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Element Atomic Number # Protons # Electrons Overall Charge Hydrogen 1 Helium 2 Lithium 3 Beryllium 4 Boron 5 Carbon 6

Describe the Properties

of the Electron

Electron

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● Complete the table below for the unreacted atoms.

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Describe the Properties

of the Electron

Electron

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● Although the number of protons and electrons in an atom start out equal they don’t stay that way.

● When an atom reacts it gains or loses electrons.

● If an atom gains or loses electrons its overall charge will no longer be zero.

● An atom will become negatively charged if it gains electrons. It will become positively charged if it loses electrons.

● An atom that has a positive or negative charge

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Describe the Properties

of the Electron

Electron

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● Watch what happens to the lithium atom when it reacts and loses an electron.

Lithium

3 Protons in the nucleus + 3 Charge

3 Electrons - 3 Charge Overall Charge

in the Unreacted Atom

Zero

Atom Loses 1 Electron

2 Electrons - 2 Charge

Overall Charge After the Reaction

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Describe the Properties

of the Electron

Electron

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● Watch what happens to the fluorine atom when it reacts and gains an electron.

Fluorine

9 Protons in the nucleus + 9 Charge

9 Electrons - 9 Charge Overall Charge

in the Unreacted Atom

Zero

Atom Gains 1 Electron

10 Electrons - 10 Charge

Overall Charge After the Reaction

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Describe the Properties

of the Electron

Electron

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● What do you think would happen to an atom if it Lost 2 electrons?

● What do you think would happen to an atom if it Gained 2 electrons?

Α The atom would have two more protons than electrons so it would become an ion with a +2 charge.

Α The atom would have two more electrons than

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Describe the Properties

of the Electron

Electron

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● You know what happens when an atom gains or loses an electron. But, why does an atom react in the first place?

● An atom reacts (gains or loses electrons) to fill the S and P orbitals or its outermost energy level.

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Describe the Properties

of the Electron

Electron - Energy Levels and Orbitals

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Nucleus

Level 1 S

Level 2 S P P P

Level 3 S P P P D D D D D

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Describe the Properties

of the Electron

Electron

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● Energy Levels determine an electron’s distance from the nucleus.

● Orbitals are subdivisions of energy levels and they determine the position of an electron within an

energy level. (2 electrons can fit in each orbital.)

● Remember, atoms will gain or lose electrons

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Describe the Properties

of the Electron

Nucleus *

Level 1 S

Level 2 S P P P

Level 3 S P P P D D D D D

Level 4 S P P P D D D D D F F F F F F F

● What will Lithium (atomic # 3) do when it reacts?

Lithium starts out with 3 electrons. 2 in the 1st level & 1 in the 2nd level

An atom’s goal is to fill the S & P orbitals of its outer energy level. There are two

ways lithium could accomplish this.

Lithium could gain 7 electrons to fill the 2nd energy level or it could lose 1 electron. This

would make the 1st level the outer level and the 1st level is already full.

An atom can’t gain electrons unless it can find another that will give. An atom can’t lose electrons unless it can find another that

will take. Therefore…

It will be easier for Lithium to lose 1 electron than to gain 7.

When Lithium loses 1 electron it will take on a +1 charge and become a lithium ion.

Lithium Ion (+1)

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Describe the Properties

of the Electron

Nucleus *

Level 1 S

Level 2 S P P P

Level 3 S P P P D D D D D

Level 4 S P P P D D D D D F F F F F F F

● What will Fluorine (atomic # 9) do when it reacts?

Fluorine starts out with 9 electrons. 2 in the 1st level & 7 in the 2nd level

An atom’s goal is to fill the S & P orbitals of its outer energy level. There are two

ways fluorine could accomplish this. Fluorine could gain 1 electron to fill the third energy level or it could lose 7 electrons.

This would make the 1st level the outer level and the 1st level is already full.

An atom can’t gain electrons unless it can find another that will give. An atom can’t lose electrons unless it can find another that

will take. Therefore…

It will be easier for Fluorine to gain 1 electron than to lose 7.

When Fluorine gains 1 electron it will take on a -1 charge and become a Fluorine ion.

Fluorine Ion (-1)

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Describe the Properties

of the Electron

● In the previous examples, Lithium lost 1 electron and became a lithium ion (+1). Fluorine gained 1 electron and became a fluorine ion (-1).

Why are these atoms still considered to be lithium and fluorine even after they react?

Α When these atoms reacted they gained or lost

electrons. But remember, it’s not the electrons that determine the element, it’s the protons. The

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Describe the Properties

of the Electron

Electron - Review

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● In an unreacted atom the number of protons equals the number of electrons

● Unreacted atoms have an overall charge of zero.

● When an atom gains or loses electrons it takes on a charge and becomes an ion.

● An atom that gains electrons is negatively charged. An atom that loses electrons is positively charged.

● Atoms gain or lose electrons to fill the S & P orbitals of their outer energy level.