CHEM 1A Review MR. BANNISTER

PART I: The Periodic Table

Atomic Number and Atomic Mass

The mass number is the atomic number

rounded to the closest whole number.

Metals vs. Nonmetals

Part II: Formula Writing

Ionic Compounds vs. Covalent Compounds (aka. Molecular Compounds)

Form between metals and nonmetals

OR

Form between metals and polyatomic ions

Form between two or more nonmetals

Ionic Compounds

• CHARGES!

Ex. Lithium nitride

Ex. Magnesium oxide

Ex. Potassium Sulfate

Li+1 N-3

K+1 (SO4)-2

Mg+2 O-2

Covalent Compounds (aka. Molecular Compounds)

• Do not worry about charges!

• Greek prefixes only!

Part III: Balancing Equations

• Rules for Balancing:– 1. Only change/add co-

efficient; never subscripts!

– 2. If a polyatomic ion appears on both sides, do not break it apart: balance it as a unit!

– 3. Balance hydrogen and oxygen last!

Part IV: Stoichiometry

• Molar Mass

– Take inventory of all atoms in your compounds – Look up the molar mass of each element – Multiple the number of each by the molar mass– Add em’ up!

Gram to Mole

• 1 mole of any substance = molar mass of that substance

• Use dimensional analysis and be sure your units cancel!