Chemistry · Periodic Classification Of Properties · NEET
Non-metals are usually brittle in the solid state (they crack or shatter when hit, they do not bend). They have a dull, non-shiny surface (no metallic lustre). They are poor conductors of heat and electricity. Many are gases (like O2, N2, Cl2) or soft solids (like sulphur) at room temperature, and they generally have low melting and boiling points. This is the opposite of metals, which are shiny, malleable, ductile and good conductors.
Metals have a 'sea of free electrons' that lets their atoms slide over each other, so metals bend. Non-metals do NOT have this free-electron sea. Their atoms are held by directional covalent bonds. When you hit a non-metal, the bonds cannot shift, so the solid cracks instead of bending. That is why solid non-metals like sulphur or iodine break apart easily.
Electric current is a flow of free electrons. In non-metals, the electrons are tightly held in covalent bonds and are not free to move. With no free electrons to carry charge, non-metals cannot conduct electricity, so they act as insulators. This is why they are poor conductors of both heat and electricity. The big exception is graphite (a form of carbon), which does conduct because it has free electrons.
Non-metals form ACIDIC oxides. For example, CO2 dissolves in water to give carbonic acid, and SO2 gives sulphurous acid. The rule for NEET: metals form basic oxides, non-metals form acidic oxides, and elements near the dividing line (metalloids) form amphoteric oxides. Oxide nature is a very common NEET question, so remember: non-metal oxide = acidic.
Non-metals are on the right side of the periodic table. They have high electronegativity and high electron gain enthalpy, so they pull electrons strongly. By gaining a few electrons, they reach the stable noble-gas configuration. So non-metals form NEGATIVE ions (anions), like Cl- or O2-, while metals lose electrons to form positive ions.
Non-metallic character INCREASES across a period from left to right, and DECREASES down a group. So the most non-metallic (except noble gases) elements sit in the top-right corner, like fluorine and oxygen. Metallic character does the exact opposite: it increases down a group and decreases across a period. Non-metallic character rises as electronegativity rises.
Almost all non-metals are poor conductors, but GRAPHITE (a form of carbon) is a well-known exception — it conducts electricity because it has delocalised free electrons. This single exception is a favourite NEET trap, so remember: 'Non-metals are non-conductors, EXCEPT graphite.'
The correct order of increasing metallic character of Na, Be, P, Mg and Si is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A non-metal is an element that is generally brittle, dull, and a poor conductor of heat and electricity, and that gains electrons to form negative ions and acidic oxides. Examples: oxygen, nitrogen, chlorine, sulphur, phosphorus, carbon.
Non-metals are found on the upper-right side of the periodic table (p-block), above and to the right of the zig-zag dividing line. Hydrogen, placed at the top-left, also behaves as a non-metal.
No. Non-metals are the opposite of metals. They are brittle, not malleable (cannot be hammered into sheets) and not ductile (cannot be drawn into wires). Solid non-metals shatter when struck.
The nature of their oxides (acidic) and the trend of non-metallic/metallic character across periods and groups are the most tested. Remember: non-metal oxide = acidic; non-metallic character increases across a period and decreases down a group.
