Non-Metals and Their Compounds

Non-Metals

Non-metals are elements that typically do not have the physical and chemical properties of metals.
Non-metals can be gases, liquids, or solids at room temperature, and are usually poor conductors of heat and electricity.
Some non-metals, such as carbon, sulphur, phosphorus, and the halogens are good reaction partners for most metals and have a more diverse range of chemical behaviour than metals.
Oxygen is a very reactive non-metal and is widely distributed in nature. It forms oxides with both metals and non-metals.

The group of non-metals known as the halogens includes fluorine, chlorine, bromine, iodine and astatine.
Halogens exist as diatomic molecules (two atoms per molecule) in their elemental form, e.g. Cl2, Br2, I2.
They are highly reactive, especially with alkali metals and alkaline earth metals, forming salts such as sodium chloride (table salt).

Non-metal oxides react with water to form acidic solutions. For example, sulphur dioxide (SO2) reacts with water to produce sulphurous acid (H2SO3).
Some non-metal oxides are considered to be pollutants. These include carbon dioxide (CO2), a greenhouse gas which contributes to global warming, and sulphur dioxide (SO2), which can lead to acid rain.

Non-metals can bond with other non-metals to form covalent compounds. An important example is water (H2O), which is a compound of the non-metals hydrogen and oxygen.
Non-metal elements like nitrogen, phosphorus, oxygen, and sulphur are vital for life on earth. They form part of many key biological molecules, including amino acids, nucleic acids, and ATP.
Carbon is another highly important non-metal. It is the primary component of organic compounds, which form the basis of all life on earth. Carbon also forms different allotropes including diamond and graphite.

Non-metals and their compounds have a significant impact on the environment.
Carbon dioxide and methane (a compound of carbon and hydrogen) are significant greenhouse gases contributing to climate change.
Nitrogen oxides and sulphur oxides contribute to air pollution and acid rain, which can damage ecosystems.
Several non-metal compounds are used as fertilisers (such as ammonium nitrate) but their overuse can lead to eutrophication, posing a threat to aquatic life.

Non-metals are typically not shiny in appearance.
They usually have lower melting and boiling points than metals.
They tend to be brittle (easy to break) when solid.
Non-metals are typically less dense than metals.
Non-metals do not have free electrons and thus are bad conductors of electricity and heat.

Non-metals react by gaining electrons to obtain a stable electronic configuration.
They form negative ions (anions).
Non-metals react with metals to form ionic compounds.
They can also react with other non-metals to form covalent compounds.
Non-metals are generally more volatile (turn into gases) than metals.
They have relatively large atomic sizes compared to metals.
Non-metals have higher electronegativity and ionisation energy than metals.