13
Compounds & Molecules Counting atoms

Compounds & Molecules Counting atoms. Counting atoms in a chemical fomula Add up the subscripts. Ca 3 P 2 = 5 atoms Don’t forget the “invisible” 1’s CaCO

Embed Size (px)

Citation preview

Compounds & MoleculesCounting atoms

Counting atoms in a chemical fomula

• Add up the subscripts.

Ca3P2 = 5 atoms

• Don’t forget the “invisible” 1’s

CaCO3 = Ca1C1O3 = 5 atoms

• Multiply anything inside parentheses by the subscript on the outside.

Ba(NO3) = 1 Ba, 2 N, 6 O = 9 atoms22

Practice

AlPO4

MgC2O4

Pb(MnO4)2

AgI

Li2S

B2(S2O3)3

67

1123

17

How Many Atoms?

Binary Compounds

Writing Chemical Formulas

Writing Chemical Formulas

• The metal (or + ion) is always written first.

• The nonmetal (or – ion) is always written last.

• The subscripts tell how many of each atom or polyatomic ion you have.

Writing Chemical Formulas

• EXAMPLE: Write the chemical formula for the ionic compound containing Al and Br.

#1 – determine the charges

Al +3

Br -1

Writing Chemical Formulas

• #2 – cross the charges. Do not carry the sign (+/-) and do not write the number 1.

Al 3

Br 1 #3 – simplify if

needed (lowest common factor)Not needed here

Writing Chemical Formulas

• You try: Mg and S Mg2S2

Simplify - MgS

Writing Chemical Formulas

• USING POLYATOMIC IONSNa and OH-1

Na+1 OH-1 NaOH

Ca and PO4-3

Ca+2 PO4-3 Ca3PO42 ???

Writing Chemical Formulas

**If the polyatomic ion gets a subscript you MUST use parentheses.**

Ca3(PO4)2

Naming Ionic Compounds

With Main Group Metals1. Name the + Ion – Name

the metal.

2. Name the - Ion - Name the nonmetal, changing the ending to –ide

Naming Ionic Compounds

Examples:

MgO

CaCl2

magnesium oxide

calcium chloride

Naming Ionic Compounds

With Polyatomic Ions

1. Name the + ion or polyatomic ion

2. Name the – ion or polyatomic ion

Examples:

NaNO3

Al2(SO4)3

sodium nitrate

aluminum sulfate