Non-Metals

Nonmetals are a category of elements that lack the metallic characteristics seen in metals. Unlike metals, which are typically shiny, dense, and good conductors of heat and electricity, nonmetals possess a set of very different properties. They are generally poor conductors of heat and electricity, making them excellent insulators.

Nonmetals exist in all three states of matter at room temperature:

• Gaseous: Many nonmetals, such as oxygen, nitrogen, and chlorine, are gases.
• Liquid: A few nonmetals, like bromine, exist in a liquid state at room temperature.
• Solid: Some nonmetals, including carbon, sulphur, and phosphorus, are solid at room temperature. These solids are usually brittle and break easily when force is applied, unlike the malleable and ductile nature of metals.

Nonmetals have high ionisation energies and high electronegativity, meaning they tend to gain or share electrons when they react with other elements. This results in the formation of covalent bonds rather than ionic bonds, which are common in metals. Due to these properties, nonmetals are essential in forming a wide variety of compounds, including organic and inorganic substances.

Exceptions,

• At room temperature, all metals, except for mercury, exist as solids. Metals have high melting points, but gallium and caesium have very low melting points. These two metals will melt if you keep them on your palm.
• Iodine is a nonmetal, but it is lustrous.
• Carbon is a nonmetal that can exist in different forms. Each form is called an allotrope. Diamond, an allotrope of carbon, is the hardest natural substance known and has a very high melting and boiling point. Graphite, another allotrope of carbon, is a conductor of electricity.
• Alkali metals (lithium, sodium, potassium) are so soft that they can be cut with a knife. They have low densities and low melting points.

Non-metals, except hydrogen, are the elements which form negative ions by the gain of electrons.

Certain elements which show properties of both metals and non metals are called metalloids or semi-metals.