Polyatomic Ions Polyatomic Ions are ions that are made up of many (poly) atoms (atomic). Polyatomic ions can be considered as “one ion”. E.g. HCO 3 -1 can be considered as “one anion”. E.g. NH 4 +1 can be considered as “one cation” Polyatomic ions form ionic compounds just like any othe r ion. E.g. K + + NO 3 -1 will form KNO 3 E.g. NH SO 4 -2 will form (NH 4 ) 2 SO 4

These are named the same way as any other ionic compound. Remember, the Cation(+) always comes before the Anion(-). But Polyatomic ions have their own name, and do not ne ed an ending change. E.g. NO 3 -1 is a Nitrate ion. KNO 3 is Potassium Nitrate. (Not Potassium Nitride)

Can you write the chemical formula of these compounds? 1.Lead (II) Sulfate 2.Barium Sulfate 3.Sodium Acetate 4.Potassium Sulfate 5.Ammonium Iodide PbSO 4 BaSO 4 NaC 2 H 3 O 2 K 2 SO 4 NH 4 I

Covalent Bonds and Covalent Molecules Polyatomic ions or molecules like CO 2 do not have ionic bonds. There are no Cations or Anions within them. These molecules form Covalent Bonds instead. Co – sharing Valence – valence electrons

A Covalent bond involves the sharing of electrons. Covalent molecules share electrons to make an Octet (stabl e).

How do we know a compound is Covalent? Covalent Compounds do not have anions and cations. Consequently, they are usually made up of non-metals. If it’s not an ionic compound, it’s covalent. Learn more about it in HS chemistry.

Can you see which compounds are covalent? 1.NaCl 2.CO 3.O 2 4.Al 2 (CO 3 ) 3 5.Mercury (II) Selenide 6.C 6 H 12 O 6 7.Magnesium Oxide 8.Carbon Dioxide Ionic Covalent Ionic Covalent Ionic

Naming Covalent Compounds (Nomenclature) 1. The first element is named first, using the elements na me. The atom in the lower group comes first. 2. Second element is named with an -ide ending. 3. Prefixes are used to denote the number of atoms. E.g. mono – 1, di – 2, tri – 3, tetra – 4 4. "Mono" is not used to name the first element. E.g. CO 2 is called Carbon Dioxide

Prefixnumber indicated mono-1 di-2 tri-3 tetra-4 penta-5 hexa-6 hepta-7 octa-8 nona-9 deca-10

Can you name these covalent molecules? 1.SiF 4 2.CO 3.N 2 F 6 4.CBr 4 5.NCl 3 6.P 2 S 3 Silicon tetrafluoride Carbon Monoxide Dinitrogen Hexafluoride Carbon Tetrabromide Nitrogen Trichloride Diphosphorous Trisulfide