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### 5.2

1. 1. IONICIONIC COMPOUNDCOMPOUND FORMATIONFORMATION 5.25.2
2. 2. IONSIONS • Octet rule: – all elements want 8 valence e-. • Cations = positive • Anions = negative, “ide”
3. 3. Opposites AttractOpposites Attract • Because cations are + and anions are – they attract each other. • This attraction forms Ionic Bonds.
4. 4. Ionic BondsIonic Bonds • Ionic bonds are very strong. • Ionic Bonds are electrically neutral. – The charges cancel each other out. – You have to have the same number of + & - • Ionic bonds form salts. – Examples: NaCl KCl CaI2 MgF2
5. 5. Monatomic or Polyatmoic?Monatomic or Polyatmoic? • MONATOMIC: 1 atom per ion • Na+1 • Cl-1 • O-2 • Al+3 • POLYATOMIC: More than one atom per ion • NH4 +1 • SO4 -2 • OH-1
6. 6. Polyatomic IonsPolyatomic Ions NH4 +1 All of the atoms in the ion act like ONE atom. The nitrogen and four hydrogens are like one atom with a +1 charge.
7. 7. Writing FormulasWriting Formulas • To write a formula, you combine the fewest positive ions and negative ions to make the total charge of
8. 8. EXAMPLESEXAMPLES
9. 9. COMBINE sodium and chlorineCOMBINE sodium and chlorine Na+1 Cl-1 To combine, we must make the charges = zero NaClTo name: use the names of the ions Sodium chlorideSodium chloride
10. 10. COMBINE calcium and bromineCOMBINE calcium and bromine Ca+2 Br-1 We will need 2 bromine ions to match the +2 of calcium Ca Calcium bromideCalcium bromide Br2
11. 11. COMBINE magnesium and nitrogenCOMBINE magnesium and nitrogen Mg+2 N-3 Can use least common denominator. Mg3 N2
12. 12. COMBINE magnesium and nitrogenCOMBINE magnesium and nitrogen Mg+2 N-3 Mg3N2 Flip flop the charges and turn them into subscripts.
13. 13. Ion formation shortcutsIon formation shortcuts • If charges are the same number drop charges and put symbols together. – The charges cancel out and become ZERO. • If charges are different numbers criss- cross the charge numbers and make a subscript on other ion.
14. 14. Polyatomics???Polyatomics??? K+1 SO4 -2 Remember, in a Polyatomic ion all the atoms act as one, even the subscripts. If they are already there, they stay there! K2SO4 COMBINE potassium and sulfate
15. 15. COMBINE aluminum and sulfateCOMBINE aluminum and sulfate Al+3 SO4 -2 Al2 SO4 3 ( ) How do we separate the subscripts so they look separate?
16. 16. Practice problemsPractice problems 1. Ammonium and chlorine 2. Aluminum and selenate 3. Lead II and bicarbonate 4. Mercury I and phosphate
17. 17. answers 1. NH4Cl Ammonium chloride 2. Al2(SeO4)3 Aluminum selenate 3. Pb(HCO3)2 Lead II bicarbonate 4. (Hg2)3(PO4)2 Mercury I phosphate