Characteristics of metals, non-metals and metalloids

An element is the simplest form of matter that cannot be split into simpler substances or built from simpler substances by any ordinary chemical or physical method. There are 110 elements known to us, out of which 92 are naturally occurring while the rest have been prepared artificially. Elements are further classified into metals, non-metals and metalloids.

Metals

All elements except hydrogen, which form positive ions by losing electrons during chemical reactions are called metals. Thus metals are electropositive elements. They are characterized by bright lustre, hardness, ability to resonate sound and are excellent conductors of heat and electricity. Metals are solids under normal conditions except for Mercury. They are ductile (can be drawn into wire) and malleable (can be beaten into very thin sheets).

Non-metals

Elements that tend to gain electrons to form anions during chemical reactions are called non-metals. These are electronegative elements. They are non-lustrous, brittle and poor conductors of heat and electricity (except graphite). Non-metals can be gaseous, liquids or solids.

Metalloids

Elements that behave like both metals and non-metals are called metalloids.

Common metal, non-metals and metalloids

Metals	Non-metals	Metalloids
Gold	Oxygen	Silicon
Silver	Carbon	Boron
Copper	Hydrogen	Arsenic
Iron	Nitrogen	Antimony
Mercury	Sulphur	Germanium
Zinc	Phosphorus

Physical Properties of Metals

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Physical State

Physical State

Metals are solids at room temperature with the exception of mercury and gallium, which are liquids at room temperature.

Lustre

Metals have the quality of reflecting light from its surface and can be polished e.g., gold, silver and copper.

Malleability

Metals have the ability to withstand hammering and can be made into thin sheets known as foils.

Ductility

Metals can be drawn into wires. 100 gm of silver can be drawn into a thin wire about 200 meters long.

Hardness

All metals are hard except sodium and potassium, which are soft and can be cut with a knife.

Valency

Metals have 1 to 3 electrons in the outermost shell of their atoms.

Conduction

Metals are good conductors because they have free electrons. Silver and copper are the two best conductors of heat and electricity. Lead is the poorest conductor of heat. Bismuth, mercury and iron are also poor conductors

Density

Metals have high density and are very heavy. Iridium and osmium have the highest densities where as lithium has the lowest density.

Melting and Boiling Point

Metals have high melting and boiling point. Tungsten has the highest melting point where as silver has low boiling point. Sodium and potassium have low melting points.

Electropositive Character

Metals are elements that have a tendency to lose electrons and form cations. They normally do not accept electrons.

To summarize: metals are electropositive in nature, lustrous, malleable, ductile, good conductors of heat and electricity and generally form basic or amphoteric oxides with oxygen.Physical-Properties-of-Non-metals">

Physical Properties of Non-metals

Physical State

Most of the non-metals exist in two of the three states of matter at room temperature: gases (oxygen) and solids (carbon). These have no metallic lustre, and do not reflect light.

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Nature

Nature

Non-metals are very brittle, and cannot be rolled into wires or pounded into sheets.

Conduction

They are poor conductors of heat and electricity.

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Electronegative Character

Electronegative Character

Non-metals have a tendency to gain or share electrons with other atoms. They are electronegative in character.

Reactivity

They generally form acidic or neutral oxides with oxygen.

Comparative Properties of Metals and Non-Metals

A detailed comparison of properties of metals and non-metals is given in table.

Property	Metals	Non-metals
State of matter	These are usually solid, except mercury, which is a liquid at room temperature. Gallium and Caesium melt below 30. So if room temperature is around 30, they may also be in liquid state	These exist in all the three states. Bromine is the only liquid.
Density	They usually have high density, except for sodium, potassium, calcium etc.	Their densities are usually low.
Melting point	They usually have a high melting point except mercury, cesium, gallium, tin, lead.	Their melting points are low.
Boiling point	Their boiling points are usually high.	Their boiling points are low.
Hardness	They are usually hard, except mercury, sodium, calcium, potassium, lead etc.	They are usually not hard. But the exception is the non-metal diamond, the hardest substance.
Malleability	They can be beaten into thin sheets.	They are generally brittle.
Ductility	They can be drawn into thin wires, except sodium, potassium, calcium etc.	They cannot be drawn into thin wires.
Conduction of heat	They are good conductors of heat.	They are poor conductors of heat.
Conduction of electricity	They are good conductors of electricity.	They are non-conductors, except for carbon in the form of graphite and the gas carbon.
Lustre	Newly cut metals have high lustre. Some get tarnished immediately.	Usually not lustrous, except iodine and diamond - the most lustrous of all the substances.
Alloy formation	They form alloys.	Generally, they do not form alloys. However carbon, phosphorus, sulphur etc. can be present in some alloys.
Tenacity	These usually have high tensile strength except sodium, potassium, calcium, lead etc.	These have low tensile strength.
Brittleness	They are hard but not brittle, except zinc at room temperature.	They are generally brittle.
Electronic configuration	They usually have 1, 2 or 3 electrons in their valence shell. The greater the number of shells and lesser the number of valence electrons, the greater is the reactivity of the metal.	They usually have 4, 5, 6 or 7 electrons in the valence shell. If it has 8 electrons, it is called a noble gas. Lesser the number of shells and greater the number of valence electrons, greater is the reactivity of the non-metal.
Ionization	They always ionize by losing electrons:	They always ionize by gaining electrons:
Charge of ions	Positively charged.	Negatively charged.
Type of valency	Metals always exhibit electrovalency.	Non-metal exhibit both electrovalency or covalency.
Deposition during electrolysis	They are always deposited at the cathode.	They are always deposited at the anode.
Redox reaction	These lose electrons and hence get oxidized.	These gain electrons and hence get reduced.
Redox agents	They are reducing agents.	They are oxidizing agents.
Nature of oxides	They generally form basic oxides, some of which are also amphoteric, such as aluminium oxide, zinc oxide, lead oxide etc.	They generally form acidic oxides. Some oxides are neutral, such as nitrous oxide, nitric oxide, carbon monoxide water etc.
Hydrides	They usually do not form hydrides except those of sodium, potassium and calcium.	They do form hydrides, e.g. NH3, PH3, HCl, HBr, HI, H2S, H2O etc.
Atomicity	These are always monatomic.	These can be mono, di, tri, or polyatomic.
Solubility	They do not dissolve in solvents except by chemical action.	They dissolve in solvents and can be re-obtained by evaporation. Example: Sulphur in carbon disulphide.
Action with chlorine	They produce chlorides, which are electrovalent.	They produce chlorides, which are covalent.
Action with dilute acids	On reaction with dilute acids they give respective salt and hydrogen.	They do not react with dilute acids.