General chemical properties of nonmetals

Non-metals

A non-metal is an element that forms negative ions by gaining electrons. This means non-metals are electronegative. In the periodic table, non-metals are found on the right-hand side and at the top of each group.

General differences between metals and non-metals

Property	Metals	Non-Metals
Electrical conductivity	Good conductors	Poor or non-conductors
Thermal conductivity	Good conductors	Poor or non-conductors
Appearance	Shiny (lustrous)	Dull (non-lustrous)
Melting and boiling points	High	Low
Density	High	Low
Malleability (can be hammered)	Malleable	Brittle (break easily)
Ductility (can be drawn into wires)	Ductile	Not ductile
Ion formation	Lose electrons (electropositive)	Gain electrons (electronegative)
Nature of oxides	Basic or amphoteric	Acidic or neutral
Halide formation	Less stable halides	Stable covalent halides (e.g. H₂O)

Chemical properties of non-metals

1. Oxidizing property of non-metals

Non-metals tend to gain electrons and form negative ions.

Examples:

$Cl + e^- \rightarrow Cl^-$

$O + 2e^- \rightarrow O^{2-}$

$N + 3e^- \rightarrow N^{3-}$

The number of electrons gained = valency of the non-metal.

So:

Chlorine (Cl) has valency 1

Oxygen (O) has valency 2

Nitrogen (N) has valency 3

2. Strong and weak oxidizing agents

Non-metals are good oxidizing agents because they accept electrons. Among the halogens (Group VII), fluorine is the strongest oxidizing agent, and the oxidizing strength decreases down the group.

Example:

$Br_2 (l) + 2e^- \rightarrow 2Br^- (aq)$

$2Fe^{2+} + Br_2 \rightarrow 2Fe^{3+} + 2Br^-$

(Bromine oxidizes $Fe^{2+}$ to $Fe^{3+}$)

3. Displacement reactions among non-metals

A more reactive non-metal can displace a less reactive one from its compound.

Examples:

• $2NaCl (aq) + F_2 \rightarrow 2NaF (aq) + Cl_2 (g)$
• $2KBr (aq) + Cl_2 \rightarrow 2KCl (aq) + Br_2 (l)$
• $2KI (aq) + Cl_2 \rightarrow 2KCl (aq) + I_2 (s)$

Non-metals can also displace hydrogen from compounds:

• $CH_4 (g) + Cl_2 (g) \rightarrow CH_3Cl (g) + HCl (g)$

Example of visible change:

• Adding Br₂ to KI solution → red color fades, and black iodine crystals form:

$2KI (aq) + Br_2 (l) \rightarrow 2KBr (aq) + I_2 (s)$