1 valence electron: the key to an element’s properties

1

Valence Electron: The Key to an Element’s Properties

Valence Electron: The Key to an Element’s Properties

2

Energy Levels and OrbitalsEnergy Levels and Orbitals

Electrons are found in orbitals (s,p,d,f).

These orbitals (s,p,d,f) are found in different energy levels.

E1: 1s E2: 2s, 2p E3: 3s, 3p etc.

Electrons are found in orbitals (s,p,d,f).

These orbitals (s,p,d,f) are found in different energy levels.

E1: 1s E2: 2s, 2p E3: 3s, 3p etc.

QuickTime™ and a decompressor

are needed to see this picture.



3

What do orbitals actually look like?What do orbitals actually look like?

Energy levels don’t look like planetary orbits.

Energy levels are just levels of energy.

The orbitals are actually just probabilities of where you can find electrons.

Energy levels don’t look like planetary orbits.

Energy levels are just levels of energy.

The orbitals are actually just probabilities of where you can find electrons.



4

What are valence electrons?What are valence electrons? Valence electrons are the electrons in the outermost energy

level.

Valence electrons are the electrons in the outermost energy level.



5

Valence Electrons and the Periodic Table

Valence Electrons and the Periodic Table

The number of valence electrons is equal to the group number!!!

Group 1 has 1 valence electron.

Group 2 has 2 valence electrons.


etc.

The number of valence electrons is equal to the group number!!!

Group 1 has 1 valence electron.



etc.



6

Why are valence electrons important?

Why are valence electrons important?

They determine how the atom will react chemically.

Elements with the same number of valence electrons will react similarly.

Therefore, elements in the same group have similar chemical properties.

ALL reactions involve changes in valence electrons.

They determine how the atom will react chemically.

Elements with the same number of valence electrons will react similarly.

Therefore, elements in the same group have similar chemical properties.

ALL reactions involve changes in valence electrons.



7

Why do we keep comparing atoms to Noble Gases?

Why do we keep comparing atoms to Noble Gases?

Noble gases are inert. That is, they don’t react.

This is because they have full energy levels (8 valence electrons). They are STABLE.

All elements want to look like Noble Gases. They will lose or gain electrons in order to have 8 valence electrons.

This is called the Octet Rule (octopus, octagon, ocho).

Noble gases are inert. That is, they don’t react.

This is because they have full energy levels (8 valence electrons). They are STABLE.

All elements want to look like Noble Gases. They will lose or gain electrons in order to have 8 valence electrons.

This is called the Octet Rule (octopus, octagon, ocho).



8

IonizationIonization

Ionization means we form an ion by losing or gaining an electron.

When we gain an electron, this is called an anion (chloride).

Cl + e- Cl-

When we lose an electron, this is called a cation (sodium)

Na Na+ + e-

Ionization means we form an ion by losing or gaining an electron.

When we gain an electron, this is called an anion (chloride).

Cl + e- Cl-

When we lose an electron, this is called a cation (sodium)

Na Na+ + e-





9

Ionization Energy (Kenny)Ionization Energy (Kenny)

Ionization energy is the amount of energy needed to remove an electron.

Na Na+ + e-

1st ionization energy is the energy to lose 1 electron.

2nd ionization energy is the energy to lose 2 electrons.

How much energy does it take to lose 1 electron in sodium? To lose 2 electrons? Look at your graph.

Ionization energy is the amount of energy needed to remove an electron.

Na Na+ + e-

1st ionization energy is the energy to lose 1 electron.

2nd ionization energy is the energy to lose 2 electrons.

How much energy does it take to lose 1 electron in sodium? To lose 2 electrons? Look at your graph.



10

Ionization Energy DiscussionIonization Energy Discussion

1. For which elements are the first ionization energies highest? Why?

2. For which elements are the first ionization energies lowest? Why?

3. For which elements are the second ionization energies highest? Why?

4. For which elements are the second ionization energies lowest? Why?

1. For which elements are the first ionization energies highest? Why?

2. For which elements are the first ionization energies lowest? Why?

3. For which elements are the second ionization energies highest? Why?

4. For which elements are the second ionization energies lowest? Why?

11

IE and Valence ElectronsIE and Valence Electrons

Ionization Energy Trend

1. The highest 1st IE occurs at the Noble Gases.

2. The lowest IE occurs at the Alkali Metals.

3. The highest 2nd IE occurs at the Halogens.

4. The lowest 2nd IE occurs at Group 6A.

Ionization Energy Trend

1. The highest 1st IE occurs at the Noble Gases.

2. The lowest IE occurs at the Alkali Metals.

3. The highest 2nd IE occurs at the Halogens.

4. The lowest 2nd IE occurs at Group 6A.

Connection to Valence Electrons1. This is because Noble Gases have a

stable (full) number of valence electrons.

2. The Alkali Metals want to lose 1 electron to look like a Noble Gas.

3. Halogens only need to lose 1 electron to look like a Noble Gas. They DO NOT want to lose more.

4. Group 6A wants to lose 2 electrons to look like a Noble Gas.

Connection to Valence Electrons1. This is because Noble Gases have a

stable (full) number of valence electrons.

2. The Alkali Metals want to lose 1 electron to look like a Noble Gas.

3. Halogens only need to lose 1 electron to look like a Noble Gas. They DO NOT want to lose more.

4. Group 6A wants to lose 2 electrons to look like a Noble Gas.

12

Ionization Energy TrendIonization Energy Trend

13

ElectronegativityElectronegativity

This is the opposite of Ionization Energy.

Electronegativity is how much an atom wants to GAIN an electron.

Cl + e- Cl-

Where is electronegativity highest?

Where is it lowest?

This is the opposite of Ionization Energy.

Electronegativity is how much an atom wants to GAIN an electron.

Cl + e- Cl-

Where is electronegativity highest?

Where is it lowest?



14

Electronegativity TrendElectronegativity Trend

15

Atomic Radius: How big are different atoms?

Atomic Radius: How big are different atoms?



16

Why do atoms get smaller even though they get heavier?

Why do atoms get smaller even though they get heavier?

As you move from left to right atoms have more protons.

This means they have more positive charge.

More positive charge means they are able to pull the electrons closer. (This is just like a magnet pulls harder as it gets closer to an object.)

From top to bottom there are more Energy Levels.

Each additional energy level increases the size of the atom.

As you move from left to right atoms have more protons.

This means they have more positive charge.

More positive charge means they are able to pull the electrons closer. (This is just like a magnet pulls harder as it gets closer to an object.)

From top to bottom there are more Energy Levels.

Each additional energy level increases the size of the atom.



17

HomeworkHomework

Revise last night’s homework for any errors. This is due next time (Monday/Tuesday).

ChemToGo p. 66-67 #1-5 will be due on Tuesday/Wednesday. You will have some time in class on Friday/Monday.

Coming soon: If you missed any notes from today or last time, you can find them at www.yourhomework.com

I will try and post the homework there every week in case you are absent or forget.

Revise last night’s homework for any errors. This is due next time (Monday/Tuesday).

ChemToGo p. 66-67 #1-5 will be due on Tuesday/Wednesday. You will have some time in class on Friday/Monday.

Coming soon: If you missed any notes from today or last time, you can find them at www.yourhomework.com

I will try and post the homework there every week in case you are absent or forget.

http://www.yourhomework.com/

http://www.yourhomework.com/

1 valence electron: the key to an element’s properties

Documents