Non–metals are the elements, which form negative ions by gaining electrons. Hydrogen, oxygen, carbon, sulphur, silicon and phosphorus are some of the non–metals or non–metallic elements.
Non–metals are poor conductors of heat and electricity, do not reflect light and have no lustre (no shine). Non–metals are brittle. The inert gases like helium, neon, argon, etc., are also non–metals.
Most of the non–metals exist in two of the three states of matter at room temperature: gases and solids. Hydrogen (H), oxygen (O), nitrogen (N), fluorine (F), chlorine (Cl) and the noble gases (rare gases), helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radioactive radon (Rn), are gases. Only bromine (Br) is a liquid at room temperature, and the rest are solids.
Non–metals have comparatively low melting points and boiling points (except graphite which has a high melting point). For example, the melting point of sulphur is 115°C, which is quite low. Non – metals have low densities. That is non–metals are light substances. For example the density of sulphur is 2 g/cm3, which is quite low. Non–metals are non – sonorous
Non–metals are very brittle and cannot be rolled into wires or pounded into sheets. Non–metals do not have free electrons. Thus the bonds between atoms in the elements are weak and they snap when stretched. The non–ductility property follows from the non–malleability or the brittleness property.
They are poor conductors of heat and electricity. In non–metals, the bonds formed are weak as there are no free electrons to share. Other than graphite, which is an allotropic form of carbon, none of the non–metals are good conductors of heat and electricity. Graphite is able to conduct electricity because of its special crystalline arrangement.
Non–metals have a tendency to gain or share electrons with other atoms. They are electronegative in character and acts as an oxidising agent.
The oxides of non–metals are acidic or neutral in nature. The non metal oxides are covalent in nature, which are formed by the sharing of electrons.The acidic oxides of non metals dissolve in water to form acids. The acidic oxides of non metals turn blue litmus solution to red.
Non– metals do not react with water and dilute acids because nonmetals are electronegitive in nature so they do not donate electrons to H+ ions to release hydrogen gas.
A more reactive non – metal displaces a less reactive non – metal from its salt solution. This is a displacement reaction. For example when chlorine is passed through a solution of sodium bromide, then sodium chloride and bromine are formed. In this displacement reaction, a more reactive non – metal chlorine is displacing a less reactive non – metal bromine from its salt solution, sodium bromide.
chlorine is an oxidizing agent because it can extract electrons from other substances, which therefore get oxidized. Chlorine itself is reduced to chloride ions
Non – metals react with chlorine to form covalent chlorides, which are non – electrolytes (do not conduct electricity). Non – metal chlorides are usually liquids or gases. For example, Hydrogen is a non–metal. So, hydrogen reacts with chlorine to form a covalent chloride called hydrogen chloride, which is a liquid.
Non–metals react with hydrogen to form covalent hydrides. The non–metal hydrides are formed by the sharing of electrons. That is, non–metal hydrides are formed by covalent bonding.
Non metals act as oxidizing agents (except carbon, which is a reducing agent).