Counting Atoms

Making Calculations

Subscripts

The small number that indicates the number of atoms of an element in a compound.

Ex. H2O

The 2 is a subscript.

Which letter does it go to, the H or the O?

Polyatomic IonsGroups of atoms that act as a single atom.

If a polyatomic Ion is used in a formula more than once, it is put in parentheses and the subscript appears outside the parentheses.

A subscript outside the parentheses indicates that all the elements inside the parentheses should be multiplied by that subscript.

Ex. Fe(OH)3

1=Iron=Fe, 3=Oxygen=O, 3=Hydrogen=H

Name / Use / FormulaCalcium Carbonate - Limestone CaCO3

Aspirin - Pain reliever C9H8O4

Magnesium Hydroxide – Found in milk of magnesia Mg(OH)2

Paradichlorobenzene – Moth crystals C6H4Cl2

Acetic acid- Found in vinegar C2H4O2

Trinitrotoluene (TNT)- Explosive C7H5(NO2)3

Calcium dihydrogen phosphate- Fertilizer Ca(H2PO4)2

Name / Use / FormulaPyrite- Fool’s gold FeS2

Sucrose- Sugar C12H22O11

Heptane- One of the items in gasoline C5H12

Sulfuric acid- Used in car batteries H2SO4

Cellulose- Found in wood C6H7O2(OH)3

Asbestos- Insulator H4Mg3Si2O9

Dichlorodiphenyltrichloroethane (DDT) C14H9Cl5Silicon dioxide- Sand SiO2

Iron oxide- Rust Fe2O3

Butane- Lighter Fluid C4H10