Question

How do you distinguish metals from nonmetals on the periodic table?

Answer 1

The metals are placed on the left-hand side and in the center of the periodic table. On the other hand, non-metals are placed on the right-hand side of the periodic table. Metals and non- metals can be distinguished from each other on the basis of few physical and chemical properties.

Complete answer:
Although there is no sharp line of distinction between metals and non-metals yet there are some distinctive differences as discussed below.

On basis of physical properties:

Property	Metals	Non-Metals
1. State of existence	Metals are mostly solid at room temperature except mercury which is liquid metal.	Non-metal exists in all the three states of matter, that is solid, liquid and gas.
2. Lustrous	Metals are lustrous and can be polished.	They are usually non-lustrous except for diamonds.
3. Hardness	Metals are generally hard	Non-metals are comparatively soft except Diamond which is a very hard substance.
4. Density	Metals have usually high densities except group 1 and group 2 metals which are light	Non-metals usually have low densities.
5. Conductivity	Metals are good conductors of heat and electricity	Non-metals are usually poor conductors of heat and electricity except graphite.
6. Malleability	They are usually malleable	Non-malleable
7. Ductility	They are ductile and sonorous	They are brittle and non-sonorous.

On basis of chemical properties:

Chemical properties	Metals	Non-metals
1. Nature of oxides	Metals form basic oxides, some are amphoteric. For example: $NaO,\,A{{l}_{2}}{{O}_{3}}$	Non-metals form acidic or neutral oxide. For example: $C{{l}_{2}}{{O}_{7}}$
2. Displacement of hydrogen from acids	Metals displace hydrogen from acids and form salts	Non-metals do not displace hydrogen from acids
3. Reaction with chlorine	Metals react with chlorine to form electrovalent chlorides.For example: $\begin{aligned} & 2Na+\,C{{l}_{2}}\to 2NaCl \\\ & Ca+C{{l}_{2}}\to CaC{{l}_{2}} \\\ \end{aligned}$	They react with chlorine to form covalent chlorides.For example: ${{P}_{4}}\,+\,6C{{l}_{2}}\to 4PC{{l}_{3}}$
4. Oxidizing and reducing agents	They act as reducing agents	They act as oxidizing agents
5. Electropositive and electronegative character	They are electropositive in character	They are electronegative in character.

Note: While a metal is a solid substance, usually hard, lustrous and opaque. On the other hand, a non-metals is a solid or gaseous material, in which the metallic properties are absent. Students should be very careful while listing down the differences as there are only a few major differences and rest are just basic differences. One should also remember that metals and non-metals have many things in common even such as they both are elements, have same atomic structure etc