Valence Electrons

​Valence Electrons

Unit 4: Modern Atomic Theory

Groups of Periodic Table

Valence Electrons

The number of valence electrons come from the HIGHEST s AND p orbital

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	​	​
​Na	​	​
General​	​	​

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	1s22s1	​
​Na	​	​
General​	​	​

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	1s22s1	1​
​Na	​	​
General​	​	​

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	1s22s1	1​
​Na	​1s22s22p63s1	​
General​	​	​

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	1s22s1	1​
​Na	​1s22s22p63s1	1​
General​	​	​

Electron Configuration for Group 1 (Main group 1)

​Element	Electron Configuration​	Number of valence e
​Li	1s22s1	1​
​Na	​1s22s22p63s1	1​
General​	​ns1	​1

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	​	​
​Al	​	​
​General	​	​

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	1s22s22p1​	​
​Al	​	​
​General	​	​

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	​1s22s22p1	3​
​Al	​	​
​General	​	​

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	1s22s22p1​	3​
​Al	​1s22s22p63s23p1	​
​General	​	​

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	​1s22s22p1	​3
​Al	​1s22s22p63s23p1​	3​
​General	​	​

Electron Configuration for Group 13 (Main Group 3)

Element​	Electron Configuration​	Number of valence e
​B	1s22s22p1​	3​
​Al	​​1s22s22p63s23p1	3​
​General	​ns2 np1	3​

Multiple Choice

What group is Beryllium (Be) in on the periodic table?

• Group 2
• Group 1
• Group 4
• Group 3

Fill in the Blanks

Based on the electron configuration of Be (1s²2s²) and its group number, it has _ valence electrons

Main Groups of Periodic Table

Group​	​1	2​	3​	4​	5​	6​	7​	8​
nsx npy	​	​	​	​	​	​	​	​
Valence e-	​	​	​	​	​	​	​	​

Main Groups of Periodic Table

Group​	​1	2​	3​	4​	5​	6​	7​	8​
nsx npy	ns1	​	​ns2 np1	​	​	​	​	​
Valence e-	​1	​	​3	​	​	​	​	​

Main Groups of Periodic Table

Group​	​1	2​	3​	4​	5​	6​	7​	8​
nsx npy	ns1	ns2​	​ns2 np1	​ns2 np2	ns2 np3​	ns2 np4​	ns2 np5​	​ns2 np6
Valence e-	​1	2​	​3	4​	5​	​6	​7	8​

Valence Electron Pattern

Write this pattern on your periodic table.

Multiple Choice

How many valence electrons does Se (#34) have?

• 5

• 8
• 4
• 6

Multiple Choice

Which group has 8 valence electrons?

• Group 1

• Group 16

• Group 17

• Group 18

Isoelectronic with Group 18

Isoelectronic - Meaning same # of electrons

• Group 18 (Noble Gases) are known for having a full octet (8 valence electrons)

• This makes them unreactive

• All atoms want to have a full octet and will gain or lose electrons in order to be like the closest noble gas

Metals vs Nonmetals

• ​Metals typically give way their valence e^- (become more positive)

• Nonmetals will typically take more valence e^- (become more negative)
  

Groups 1,2, and 13 (first 3 main groups) give away their valence e^-

Group​	​# of Valence e-	Charge​
​1	​	​
2​	​	​
13​	​	​

Groups 1,2, and 13 (first 3 main groups) give away their valence e^-

Group​	​# of Valence e-	Charge​
​1	​1	​+1
2​	​2	​+2
13​	​3	​+3

Group 14 (Main group) 4 will either gain or lose their valence electrons and become more positive or negative.

​Group	​# of valence e-	​Charge
​14	​	​

Group 14 (Main group) 4 will either gain or lose their valence electrons and become more positive or negative.

​Group	​# of valence e-	​Charge
1​4	​4	+/- 4​

Groups 15,16,17 (Main Groups 5,6,7) will gain and become more negative

Group​	​# of Valence e-	Charge​
1​5	​	​
16	​	​
17	​	​

Groups 15,16,17 (Main Groups 5,6,7) will gain more valence electrons and become more negative

Group​	​# of Valence e-	Charge​
1​5	​5	​-3
16	​6	​-2
17	​7	​-1

Oxidation State

• The charge on the ion once it loses its valence electrons, is called its oxidation state.

• This will become important when we start making compounds for chemical reactions.

Electron Dot Diagram

Shows the valence electrons for atoms. Place valence electrons around the SYMBOL of the element. Fill s orbital first, then p orbitals 1 at a time

X

​s

​p

​p

​p

Example: Phosphorus

1. Determine number of valence electrons:

2. Write the symbol

3. Draw dots around to represent the number of valence electrons. Fill s orbital first, then 1 at a time for p orbitals

Example: Phosphorus

1. Determine number of valence electrons:

2. Write the symbol

3. Draw dots around to represent the number of valence electrons. Fill s orbital first, then 1 at a time for p orbitals

P

s

p

p

p

Draw

Draw the electron dot diagram for Bromine (Br).

Electron Configuration for ions

Ions

• Atoms can exist as ions (having a charge) which means their number of electrons is NOT equal to the number of protons

• We can write the electron configuration for ions, once we take into account the number of electrons an ion has

Multiple Choice

How many electrons does Al⁺³ have?

• 9
• 11

• 10
• 13

Multiple Choice

What neutral atom also has 10 electrons?

• Neon (Ne)
• Oxygen (O)
• Argon (Ar)
• Carbon (C)

What is the electron configuration for Al⁺³