Ionic Bonds & Formulas NaCl

Na+ NaCl Cl– Ionic Compounds: Ionic Bonds: (e-s completely separate) -composed of + cations and – anions but… they are electrically neutral overall (net charge = 0) Na+ NaCl Cl– Ionic Bonds: electrostatic (Coulombic) attraction between + & – ions in ionic compounds.

NaCl CaS PbO2 Ca2S2 Pb2O4 1+ 1– 2+ 2– 4+ 2– + – + – – + – + + – + – Binary Compounds: contain only two different atoms Chemical Formula: shows type & number of atoms in substance. Formula Unit: the lowest whole-number ratio of atoms in an ionic compound. + – + – – + – + + – + – 1+ 1– 2+ 2– 4+ 2– NaCl CaS PbO2 Ca2S2 Pb2O4

Writing Formulas of Ionic Compounds: 1. Write symbol of cation(+), then anion (–). (That is metal first and then non-metal). 2. Write charge of each ion as a superscript. 3. Write subscripts to balance the charges (crisscross charges) 4. Erase charges (neutral compound). potassium oxide magnesium nitride K+ + 2– 2+ Mg2+ N3– K O Mg 3– N Mg2+ N3– K+ O2– Mg2+ K2O Mg3N2 +2 –2 +6 –6

Writing Formulas of Ionic Compounds: NAME FORMULA Ca2+ O2– CaO calcium oxide _________ aluminum oxide _________ magnesium phosphide _________ lithium sulfide _________ (lowest ratio) Al3+ O2– Al2O3 Mg2+ P3– Mg3P2 Li+ S2– Li2S

1. Which chemical formula is correct? KO MgS2 CaO Na2Br Quick Quiz! 1. Which chemical formula is correct? KO MgS2 CaO Na2Br

2. Which chemical formula is incorrect? KF2 CaS MgO NaBr Quick Quiz. 2. Which chemical formula is incorrect? KF2 CaS MgO NaBr

charges vary but always + 1+ 2+ 3+ 3– 2– 1– transition metals charges vary but always +

– Cl Lewis dot diagrams [Na]+ AlCl3