Unit 4 Notes: Valence Electrons, Cations & Anions

(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

(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…

(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

(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

(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

(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

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

(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

(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

(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

(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

(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

(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: