Valence Electrons and Ions

1
Valence Electrons and Ions

• Unit 3

2
Valence Electrons

• Electrons in the outermost energy levels
• Involved in chemical bonding
• Remember all elements want 8 valence e-
• A groups roman numeral
• B groups assume 2 valence e-
• (unless told otherwise)
• EX How many F electrons are important to
  chemical bonding ?

7
3
Lewis Dot Structures

• Represent valence electrons

Examples
Ca F Ba W N
4
Ions

• Atom that has a () or (-) charge due to gaining
  or losing electrons
• Anion ( - ) gained e-
• Cation ( ) lost e-
• Why is the cation when it lost e- ?
• Monatomic ions containing only one atom

5
Oxidation Numbers

• Overall charge on an ion after it has gained or
  lost electrons
• 1A has an over all charge of 1
• Heres why
• Na
• 11 p
• 11 e -
• 0

6
Oxidation Numbers

• 1A has an over all charge of 1
• When it bonds it loses its 1 outer electron
  leaving it with 10 e-
• Na
• 11 p
• 10 e -
• 1

7
Put these on your periodic Table
1A ( 1 ) 2A ( 2) 3A ( 3) 4A (/-
4) 5A (-3) 6A (-2) 7A (-1) 8A (0)
B groups Assume a 2 charge unless told
otherwise EXCEPTION Ag 1, Cd 2, Zn 2, Al
3, Sc 3
8
EX

• How many protons and electrons are in each ion?
• Br 1-
• Ca 2
• P 3-