Nomenclature Ionic Compounds Held together by ionic bonds

Nomenclature

Ionic Compounds • Held together by ionic bonds. • What are ionic bonds? – Between metals and nonmetals – Transfer of electrons between atoms. – Attraction between oppositely charged ions.

Ionic Compounds • Some examples are: – – Na. Cl Mg. Cl 2 KBr Li 2 O • These are all bonds between cations (positive ions) and anions (negative ions).

Naming Ionic Compounds • Binary Ionic Compounds – The metal will be your cation. Its name comes first. – The non-metal will be your anion. Its name comes second, but undergoes a slight change. • Change the ending to –ide. • Example: Chlorine Chloride, Nitrogen Nitride • Li 2 O ide Lithium + Oxygen Metal Non-Metal

Practice • Name the following ionic compounds: – – – Mg. Cl Rb 2 S Be. F 2 Cs 3 N KI Magnesium Chloride Rubidium Sulfide Beryllium Fluoride Cesium Nitride Potassium Iodide – In ionic compounds, the subscripts do NOT affect the name of the compound.

Naming Ionic Compounds • Polyatomic Ions NAC book page 235 – Ions made of multiple atoms. – Name using an ion chart, but otherwise name the same as binary compounds. – Examples: – Mg. CO 3 = Magnesium Carbonate – (NH 4)2 SO 4 = Ammonium Sulfate

Writing Formulas from Names • The key to writing correct ionic formulas is to balance your positive and negative charges. We want a neutral molecule. • The charge of the cation becomes the subscript of the anion. • The charge of the anion becomes the subscript of the cation.

Writing Formulas From Names • Sodium Chloride • Sodium = Na+, Chlorine = Cl- Na 1 Cl 1 Na. Cl

Writing Formulas from Names • Magnesium Fluoride • Magnesium = Mg 2+, Fluorine = F- Mg 1 F 2 Mg. F 2 **Do not include the charge in your formula.

Why does this work? • Magnesium Fluoride Magnesium Fluorine -1 2+ -1 2 + -2 =0

Ionic Naming using Transition Metals (and Tin and Lead) • The charges of transition metals can vary. • A transition metal can have different charges depending on the situation. • You can use the formula to determine its charge in a specific molecule.

Example #1 • Cu. I 2 • We know Iodine has a charge of -1, but we have to determine the charge of copper. Copper Iodine +? -1 -1 ____ + -2 So… the charge of Copper in this molecule must be +2. The name is written: Copper (II) Iodide =0

• Mn 2 Cl 4 Example #2 Manganese Chlorine +? -1 We are trying to find the charge of one Manganese atom. The charge of one Manganese atom is +2, so the formula for Mn 2 Cl 4 is: Manganese (II) Chloride -1 -1 2 x ? + -4 =0

Practice • Ni. S 2 • Ag. F • Sn 3 N 4 Lead (III) Phosphide • Titanium (IV) Chloride • Chromium (II) Iodide •

Writing Formulas from Names • You can write the formulas for ionic compounds using transition metals the same as ionic compounds using alkali or alkaline earth metals. Mercury (I) Sulfide Mercury = Hg+, Sulfur = S 2 Hg 2 S

Molecular Compounds • Held together by Covalent bonds. – Between non-metals. – Sharing of electrons • Examples: – H 2 O – C 2 H 4 – SO

Naming Molecular Compounds • Begin by writing the name as you would a binary ionic compound. • Add prefixes to each name which tell you how many of that atom are in the molecule. – If there is only one atom of the first element in the molecule you can leave out the “mono” prefix on the first element only. Prefix Definitions Mono = 1 Di = 2 Tri = 3 Tetra = 4 Penta = 5 Hexa = 6 Hepta = 7 Octa = 8 Nona = 9 Deca = 10

Practice • P 2 S 3 • H 2 O • CO • N 2 O 4

Metal + Non-metal or presence of polyatomic ion Includes Transition metal, Lead or Tin Includes Alkali or Alkaline Earth Metal Must include charge of transition metal in parentheses. Name using binary ionic rules. No charge in parentheses needed. 2 non-metals (Carbon, Silicon, elements in groups 15 -17, or Hydrogen) Name using prefixes. Charges are not relevant.