Metals and Non-metals

Quickly browse through questions and notes on related topics. You can also download and read this topic offline.

• Questions
• Summary

Chemical properties are characteristics of a material that becomes evident when the material undergoes a chemical reaction or chemical change.

Chemical properties cannot be determined by touching or viewing a sample.

chemical properties help in classification of metal and its compounds.

Example of chemical properties:

1. Reactivity with other chemicals
2. Oxidation states
3. Toxicity
4. Heat of combustion
5. Coordination number
6. Flammability
7. Enthalpy of formation
8. Heat of combustion
9. etc.

Reactive metals can displace less reactive metals from their compounds in solution or molten form.

Metal A + Salt solution of B → Salt solution of A + Metal B

Fe + CuSO₄ → FeSO₄ + Cu

A series of metallic elements arranged in the increasing or decreasing order of their reactivity is called a reactivity series of metals.

In the reactivity series, copper, gold, and silver are at the bottom and hence least reactive. These metals are known as noble metals.

K
Na
Ca
Mg
Al
Zn
Fe
Pb
H
Cu
Hg
Ag
Au

Almost all metals combine with oxygen to form metal oxides.

Metal + Oxygen → Metal oxide

For example, when copper is heated in air, it combines with oxygen to form copper(II) oxide, a black oxide.

Similarly, aluminium forms aluminium oxide.

4Al + 3O₂ → 2Al₂O₃

Different metals show different reactivities towards O₂.

1. Na and K react so vigorously that they catch fire if kept in open so they are kept immersed in kerosene.
2. Surfaces of Mg, Al, Zn, Pb are covered with a thin layer of oxide which prevent them from further oxidation.
3. Fe does not burn on heating but iron fillings burn vigorously.
4. Cu does not burn but is coated with black copper oxide.
5. Au and Ag do not react with oxygen.

Amphoteric Oxides: Metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.

Examples :

Al₂O₃ + 6HCl → 2AlCl₃ + H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Metals react with acids to give a salt and hydrogen gas.

Metal + Dilute acid → Salt + Hydrogen

Reaction of aluminium with dilute hydrochloric acid: Aluminium chloride and hydrogen gas are formed.

2Al + 6HCl → 2AlCl₃ + 3H₂

Reaction of zinc with dilute sulphuric acid: Zinc sulphate and hydrogen gas are formed when zinc reacts with dilute sulphuric acid. This method is used in the laboratory to produce hydrogen gas.

Zn + H₂SO₄ → ZnSO₄ + H₂

Reaction of sodium metal with dilute acid: Sodium metal gives sodium chloride and hydrogen gas when react with dilute hydrochloric acid.

2Na + 2HCl → 2NaCl + H₂

Reaction of potassium with dilute sulphuric acid: Potassium sulphate and hydrogen gas are formed when potassium reacts with dilute sulphuric acid.

2K + H₂SO₄ → K₂SO₄ + H₂

Reaction of magnesium metal with dilute hydrochloric acid: Magnesium chloride and hydrogen gas are formed when magnesium reacts with dilute hydrochloric acid.

Mg + 2HCl → MgCl₂ + H₂

Copper, gold and silver are known as noble metals. These do not react with water or dilute acids.

Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO₃ is a strong oxidising agent. It oxidises the H₂ produced to water and itself gets reduced to any of the nitrogen oxides (N₂O, NO, NO₂). But magnesium (Mg) and manganese (Mn) react with very dilute HNO₃ to evolve H2 gas.

Metals form respective metal hydroxide and hydrogen gas when react with water.

Metal + Water → Metal oxide + Hydrogen

Metal oxide + Water → Metal hydroxide

Metal oxides that are soluble in water.

Most of the metals do not react with water. However, alkali metals react vigorously with water.

Metals like potassium and sodium react violently with cold water. In case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.

2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g) + heat energy 

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂ (g) + heat energy

The reaction of calcium with water is less violent. The heat evolved is not sufficient for the hydrogen to catch fire.

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.

Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen.

Metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

2Al(s) + 3H₂O(g) → Al₂O₃(s) + 3H₂(g)

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

Metals such as lead, copper, silver and gold do not react with water at all.