1. Ionic Bonds & Formulas NaCl

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

3. CaSPbO 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. Na 2 Cl 2 Ca 2 S 2 Pb 2 O 4 1+ 1– 2+ 2– 4+ 2– + + + + + + – – – – – –

4. Writing Formulas of Ionic Compounds: 1. Write symbol of cation (+), then anion (–). 2. Write charge of each ion as a superscript. 3. Write subscripts to balance the charges (crisscross charges) 4. Erase charges (neutral compound). K2OK2OMg 3 N 2 K potassium oxidemagnesium nitride O + 2– Mg N 2+ 3– K+K+ K+K+ O 2– Mg 2+ N 3– Mg 2+ N 3– +2 –2+6 –6

5. calcium oxide _________ aluminum oxide _________ magnesium phosphide _________ lithium sulfide _________ Li + S 2– Writing Formulas of Ionic Compounds: NAMEFORMULA CaO (lowest ratio) Al 2 O 3 Mg 3 P 2 Li 2 S Ca 2+ O 2– Al 3+ O 2– Mg 2+ P 3–

6. 1. Which chemical formula is correct? A.KO B.MgS 2 C.CaO D.Na 2 Br Quick Quiz!

7. 2. Which chemical formula is incorrect? A.KF 2 B.CaS C.MgO D.NaBr Quick Quiz.

8. 1+2+ 3+ 3–2– 1– charges vary but always + transition metals

9. AlCl 3 Cl – [Na] + Lewis dot diagrams