1.1 - Formulae and Equations

Question 1

Oxidation Numbers

Answer 1

The oxidation number of an atom in a molecule is the charge it would have if the electrons in each of its bonds belonged to the more electronegative element.

Question 2

Rules for Oxidation Numbers

Answer 2

The oxidation number of an uncombined element in its natural state is zero

Question 3

Rules for Oxidation Numbers

Answer 3

The sum of the oxidation states in a neutral substance (covalent or ionic) is always zero

Question 4

Rules for Oxidation Numbers

Answer 4

In an individual polyatomic ion, the sum of the oxidation numbers is equal to the ionic charge.

Question 5

Rules for Oxidation Numbers

Answer 5

Group 1 metals always show an oxidation number of +1

Question 6

Rules for Oxidation Numbers

Answer 6

Group 2 metals always show an oxidation number of +2

Question 7

Rules for Oxidation Numbers

Answer 7

Fluorine always has an oxidation number of -1

Question 8

Rules for Oxidation Numbers

Answer 8

Oxygen nearly always has an oxidation number of -2 (except when bonded to fluorine and in peroxides and in super-oxides such as Na₂O₂ and KO₂

Question 9

Rules for Oxidation Numbers

Answer 9

Hydrogen usually shows an oxidation number of +1, except when bonded to group 1 e.g. NaH