Naming and Writing Formulas

Types of Compounds There are two types of compounds. Ionic: Covalent: a metal and an nonmetal Covalent: contain two nonmetals

Ionic Compounds Must contain a positive ion (cation) and negative ion (anion). The cation (metal) is written first, the anion (nonmetal) is written second. The total charge on the compound must equal 0.

Naming Binary Ionic Compounds #1 – Name the metal (written on periodic table) #2 – Name the nonmetal, changing the ending to –ide. Examples: MgO CaCl2 NaBr Sr3P2 magnesium oxide calcium chloride sodium bromide strontium phosphide

Writing Formulas The subscripts tell how many of each atom you have. (The overall charge must equal zero!!) EXAMPLE: Write the chemical formula for the compound containing Al and Br. #1 – determine the charges Al+3 Br-1

Al+3 Br-1 AlBr3 #2 – cross the charges. #3 – Write the formula, simplify if needed AlBr3 1 3

Try this one… Write the chemical formula for the compound containing Mg and S #1 – determine the charges Mg+2 S-2

Mg+2 S-2 Mg2S2 MgS #2 – cross the charges. #3 – Write the formula, simplify if needed Mg2S2 MgS 2 2

Ionic Compounds with Polyatomic Ions #1 – name the 1st part of the compound #2 – name the 2nd part If it is a polyatomic ion, DO NOT change the ending If it is a nonmetal, change to –ide. Examples: CaCO3 Na3SO4 (NH4)2S Calcium carbonate Sodium sulfate Ammonium sulfide

Writing Formulas: Na+1 OH-1 NaOH Same rules apply, except if the polyatomic ion gets a subscript you MUST use parentheses around it. Example: Write the formula for sodium hydroxide. Na+1 OH-1 NaOH 1 1

Writing Formulas for Polyatomic Compounds Calcium phosphate Ca+2 PO4-3 Ca3(PO4)2 3 2

Aluminum nitrite Al+3 NO2-1 Al(NO2)3 1 3

Compounds Containing Metals with Variable Charges

Variable Charges (Transition Metals) Metals in Group 1, Group 2, Zinc (+2), Silver (+1) have one charge. The rest have variable charges so we have to tell what charge the ion has in our compound when we name it.

Naming #1 – Name the metal. #2 – Add a roman numeral telling the charge on the metal in parentheses. I-1 II-2 III-3 IV-4 V-5 VI-6 VII-7 #3 – Name the negative ion as before.

Example CrO O is a -2 charge To make a neutral compound, Cr must be a +2. Chromium (II) oxide

FeCl3 Cl is a -1 charge There are 3 chlorine ions  -3 The ONE Fe must be a +3 Iron (III) chloride

CoCO3 Carbonate is a -2 Co is a +2 Cobalt (II) carbonate

Ni3(PO4)2 Phosphate = -3 x 2 = -6 There are 3 nickel atoms so each one = +2 to equal +6 Nickel (II) phosphate

Mn(SO4)2 Mn2(SO4)4 Mn(SO4) Sulfate is -2, so the Manganese = +4 Manganese (IV) sulfate Mn2(SO4)4 Mn(SO4)

Writing formulas: Rules are the same as before.

copper (III) oxide Cu+3 O-2 Cu2O3 2 3

Manganese (IV) sulfide Mn+4 S-2 Mn2S4 MnS2 4 2

Iron (II) nitrate Fe+2 NO3-1 Fe(NO3)2 1 2