Oxidation numbers rules

In this molecule which element is an anion?

HCl

• H

• Cl

• None

• Both

Give the oxidation number of Fe⁺²

• 0

• 1

• -2

• +2

Give the oxidation number of H₂

• 0

• 1+

• -2

• +2

In the following molecule which is element is a cation?

Mg(OH)₂

• Mg

• O

• All of them

• None

Elements from group VIIA or 17 have a usual oxidation number of

• +1

• -1

• 0

• -2

Hydrogen when combined with metals has an oxidation number of

• +1

• -1

• 0

• -3

Fluorine when combined with elements has an oxidation number of

• -1

• 0

• -2

• -3

Calculate the oxidation number of manganese is KMnO₄

• +5

• +9

• +7

• +3

Which is the oxidation number of calcium in CaCl₂

• +1

• -2

• +4

• +2

CoF₃

• -1

• +5

• +3

• -7