Writing Ionic Cmpds

Compound Name

Metal (+)

Nonmetal (-)

Criss-cross to get Chemical Formula

(divide thru by 2 or 3 if can reduce)

Sodium Chloride

Na1+

Cl1-

Na1+1 Cl1-1 = NaCl

Aluminum Chloride

Al3+

Cl1-

AlCl3

Calcium Oxide

Ca2+

O2-

Ca2+2 O2-2

(divide thru by 2 to reduce) = CaO

Aluminum Phosphide

Al

P

Magnesium Oxide

Mg

O

Cesium Fluoride

Cs

F

Strontium Nitride

Sr

N

Lithium Sulfide

Li

S

Calcium Chloride

Aluminum Fluoride

Potassium Nitride

Sodium Sulfide

Lithium Oxide

Calcium Oxide

Zinc Oxide Zn is a transitional metal with only one charge possible

Silver Iodide Ag is a transition metal with only one charge possible

Iron (II) Oxide Fe is a transition metal with more than one possible charge- the Roman Numeral gives the charge on Fe

Iron (III) Oxide

Lead (IV) Oxide lead is a post-transition metal with more than one possible charge- the Roman Numeral gives the charge on Pb

Calcium hydroxide this compound includes the polyatomic ion OH-

Ca

OH

Example: If polyatomic ion AX3 gets a NEW subscript, like 2 put ion inside ( ) then subscript outside (AX3)2