Chemical Formulae

monoatomic element

• N₂

• CO

• Kr

• O₂

Match the correct answer.

• polyatomic molecule of element

• CO

• diatomic molecule of compound

• O₃

• diatomic molecule of element

• O₂

What is the total number of atoms in glucose, C₆H₁₂O₆?

What is the total number of elements in iron(III) phosphate, Fe₃(PO₄)₂

• 3

• 8

• 12

• 13

Valency of an element is the number of valence electrons that must be gained, lossed or shared to achieve a complete valence electron shell.

What is the valency of the following elements?

• 1

• O

• 4

• Li

• 3

• N

• 2

• C

• 2

• Ca

The ions of transition metals can have more than 1 valency. The valency is indicated using Roman numerals in bracket.

What is the valency of the following ions?

• 2

• titanium(IV)

• 1

• silver ion

• 3

• iron(III) ion

• 4

• copper(II) ion

Valency of a polyatomic ion is the overall charge on the ion.

The valency of ammonium ion, NH₄⁺ is

The valency of hydroxide ion, OH^- is

The valency of nitrate ion, NO₃^- is

The valency of sulfate ion, SO₄^2- is