1. Unit 4 Notes: Valence Electrons, Cations & Anions

2. (1) Electrons & Shells Electrons:
Negatively charged subatomic particles
Circle around nucleus
Electron Shells:
Probable areas with electrons
Hold certain # of electrons
Draw them as circles around Nucleus

4. (2) # of Electrons / Shell
1st Shell  can hold only 2
2nd Shell  can hold only 8
Every other Shell  Multiple of 8
EXAMPLE: Draw an atom of Sodium…

5. (3) Valence Electrons Valence Electron:
Outermost electron/s of an atom
Found in last shell
Group # = # of Valence Electron/s
EXAMPLE: How many valence electrons do these have?
Lithium = Group ______ = _____ valence electrons
Aluminum = Group _____ = _____ valence electrons
Neon = Group _____ = _____ valence electrons

7. (4) Flame Tests Valence Electrons can…. Flame Tests: Gain energy
Lose energy
Form bonds between atoms
Flame Tests:
Light element on fire
Look for unique color
Color = Amount of heat energy gained + lost by valence electron/s

9. (5) Stable or Not Stable Stable: Atom has 8 valence electrons
Will not react or bond with other atoms
Not Stable:
Atom has less than 8 valence electron (1-7)
Will react or bond with other atoms to become stable
Groups 1-3 will lose v.electrons
Groups 5-7 will gain v.electrons

11. (6) Gaining & Losing Groups 1-3 = Lose Their Valence Electrons
Easier to lose 1-3, than gain 5-7 v.electrons
Lose Electron = Become (+) Charged
Group 4 = Can Gain OR Lose Their Valence Electrons
Groups 5-7 = Gain More Valence Electrons
Easier to gain 1-3, than lose 5-7 v.electrons
Gain Electron = Become (-) Charged

13. (7) Ions Ion = Charged Atom
Atoms become charged when they gain/lose valence electrons
Types of Ions:
Cations
Anions

14. (8) Cations Cations = Positively Charged Ions
They were atoms that LOST their v.electrons
Groups 1-3
Elements & Charges:
Group #
# of V.E. Lost
Charge 1A 1 +1 2A 2 +2 3A 3 +3

16. (9) Anions Anions = Negatively Charged Ions
They were atoms that GAINED more v.electrons
Groups 5-7
Elements & Charges:
Group #
# of V.E. Gained
Charge 5A 3 -3 6A 2 -2 7A 1 -1

17. (10) Special Groups Group 4 Elements:
Can gain or lose because they have 4 v.electrons
Can be cations or anions
The Noble Gases:
All Group 8A elements are stable
They will never be cations or anions

18. (11) Forming Compounds Compound = 2 or elements bonded together
Stable compounds should have ZERO CHARGE.
Cations bond with Anions to form stable compounds.
1 Na bonds with 1 Cl to form NaCl
2 K bond with 1 O to form K2O

20. (12) Polyatomic Ions Name Chemical Formula Charge Hydroxide OH- -1
Nitrate
NO3-
Carbonate
CO32- -2
Sulfate
SO42-
Phosphate
PO43- -3
Bromate
BrO3-
Ammonium
NH4+ +1

21. (13) FORMULA EXAMPLES: Write the formula for Li bonding with Br:
Write the formula for Al bonding with O:
Write the formula for Sr bonding with I: