METAL AND NON-METALS

Like their physical properties, the chemical properties of metals and non-metals are different.

Chemical Properties of Metals

Reactions of Metals with Oxygen: Metals react with oxygen to form metal oxides, which are basic in nature. Some metal oxides react with water to form alkalis. For example,

4Na + O₂ → 2Na₂O

Na₂O + H₂O → 2NaOH

Sodium, potassium, and lithium metals are very reactive. They react vigorously with oxygen present in the air. That is why they are stored under kerosene oil to protect them from oxygen, moisture, and carbon dioxide in the air. Metal oxides which show basic as well as acidic behaviour are known as amphoteric oxides. Examples: Aluminium oxide and zinc oxide. They react with both acids and bases to form salt and water. Silver and gold do not react with oxygen even at high temperatures.

Reaction of Metals with Water: When a metal reacts with water (cold or hot), it forms metal hydroxide and hydrogen gas. When a metal reacts with steam, the products are metal oxide and hydrogen gas. Sodium and potassium react vigorously with water, producing a lot of heat. Lead, copper, silver and gold do not react with water or steam. Only those metals displace hydrogen from water which are above hydrogen in the reactivity series shown in the table below.

Reactions of Metals with Dilute Acids: Metals react with dilute acids to form salt and hydrogen gas. Metals like copper, silver, and gold, which are less reactive than hydrogen, do not react with dilute acids. Metals which are above hydrogen in the reactivity series react with dilute acids.

Aqua- regia, a mixture of one part of concentrated nitric acid and 3 parts of concentrated hydrochloric acid, is a highly corrosive, fuming liquid. It can dissolve all metals, including gold and platinum. However, concentrated nitric acid and hydrochloric acid separately cannot dissolve gold and platinum.

The Reactivity (or Activity) Series of Metals

The arrangement of metals in order of decreasing reactivities is called reactivity series of metals. The most reactive metal (potassium) is placed at the top, whereas the least reactive (gold) at the bottom of the series (see the table below).

Less reactive metals (like silver and gold) are usually found in free state in nature. Metals which are more reactive than hydrogen can displace hydrogen from its compounds, like water and acids, to form hydrogen gas, whereas metals less reactive than hydrogen cannot do so.

Reaction of Metals with Salt Solutions: A more reactive metal displaces a less reactive metal from its salt solution. For example,

CuSO₄ (aq) + Fe (s) → FeSO₄ (aq) + Cu (s)

When an iron rod is placed in copper sulphate solution, then the blue colour of copper sulphate solution fades slowly and a reddish-brown layer of copper gets deposited on the iron rod. This happens because iron is more reactive than copper. If, on the other hand, a copper rod is placed in FeSO4 solution, then no reaction occurs because of the lower reactivity of copper as compared to iron.

Reaction of Metals with Chlorine: Metals react with chlorine to form metal chlorides which are ionic compounds. For example,

2Na + Cl₂ → 2NaCl

These metal chlorides are electrolytes, i.e., they conduct electricity in solution or in molten state.

Reaction of Metals with Hydrogen: Most of the metals do not react with hydrogen. Only reactive metals like sodium, potassium, calcium and magnesium react with hydrogen to form metal hydrides.

Ca + H₂ → CaH₂

Metal hydrides are ionic compounds in which hydrogen is present in the form of hydride ion (H^-), an anion.

Chemical Properties of Non-Metals

Reaction of Non-Metals with Oxygen: Non-metals combine with oxygen to form acidic oxides (like carbon dioxide and sulphur dioxide) or neutral oxides (like water and carbon monoxide). Non-metal oxides are covalent in nature. Acidic oxides of non-metals dissolve in water to form acids. For examples,

S + O₂ → SO₂

SO₂ + H₂O → H₂SO₃

Neutral oxides of non-metals do not produce an acid with water.

Reaction of Non-Metals with Water: Non-metals do not react with water to produce hydrogen gas.

Reaction of Non-Metals with Dilute Acids: Non-metals do not react with dilute acids. No hydrogen gas is evolved when a dilute acid is added to a non-metal.

Reaction of Non-Metals with Salt Solutions: A more reactive non-metal displaces a less reactive non-metals from its salt solution. For example,

2KI + Cl₂ → 2KCl + I₂

Reaction of Non-Metals with Chlorine: Non-metals react with chlorine to form covalent chlorides which do not conduct electricity. Non-metal chlorides are usually liquids or gases. For example,

H₂ + Cl₂  → 2HCl

Reaction of Non-Metals with Hydrogen: Non-metals react with hydrogen to form covalent hydrides. For example,

N₂ + 3H₂ → 2NH₃

Non-metal hydrides are liquids or gases. They do not conduct electricity.

Uses of Metals

• Aluminium, copper and iron are used to make utensils and industrial equipment.
• Copper and aluminium are used to make electrical wires.
• Zinc is used for galvanising iron to protect it from rusting.
• Chromium and nickel are used in the manufacture of stainless steel and for electroplating iron and steel objects.
• Mercury is used in thermometers.
• Aluminium foils are used in packaging of medicines, cigarettes and food materials.
• Silver foils are used to decorate sweets.
• Gold and silver are used to make ornaments.
• Lead is used in car batteries.
• Zirconium is used in making bullet-proof alloy steels.
• Sodium, zirconium and titanium are used in atomic energy and space science projects.
• Many metals are used as catalysts in chemical reactions.

Uses of Non-Metals

• Hydrogen is used in the manufacture of Vanaspati ghee.
• Hydrogen is used in the manufacture of ammonia. Compounds obtained from ammonia are used as fertilizers.
• Liquid hydrogen is used as rocket fuel.
• Carbon (graphite) is used for making the electrodes of dry cells.
• Nitrogen is used as a refrigerant to preserve food materials. It is also used to provide an inert atmosphere. It is filled in electric bulbs.
• Nitrogen is used in the manufacture of ammonia, nitric acid, and fertilizers (like urea, ammonium nitrate, ammonium sulphate, ammonium phosphate, calcium ammonium nitrate (CAN), etc.) Liquid ammonia is used as a refrigerant in ice factories and cold storages.
• Trinitro toluene (TNT) and nitroglycerine (compounds of nitrogen) are used as explosives.
• Sulphur is used in the manufacture of sulphuric acid.
• Sulphur is used in the vulcanisation of rubber.
• Sulphur is used as a fungicide and for making gun powder.