Metals and Non-metals | Study

Elements are classified as metals and non-metals based on different properties. The properties of metals and non-metals are given in the form of table below-

Chemical Properties of Metals

• Metals react with air or oxygen to form metal oxide.

For Example, Copper reacts with oxygen to form copper oxide.

Metal + O₂ → Metal oxide

2Cu + O₂ → 2CuO

4Al + 3O­₂ → 2Al₂O₃

• Oxides of metals can react with both acids and bases to produce salt and water. Such oxides are known as Amphoteric Oxides.

Al₂O₃ + 6HCl → 2AlCl₃ + H₂O

• Metals also reacts with water to form metal oxide. Metal oxide in turn can react with water to form metal hydroxide. For Example

2Na + 2H₂O → 2NaOH + 1H₂

2Al + 3H₂O → Al₂O3 + 3H₂

• Metals also reacts with dilute acids to form salt and hydrogen. For example, magnesium reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen.

Metal + Acid → Metal Salt + Hydrogen

Mg + 2HCl → MgCl₂ + H₂

Chemical Properties of Nonmetals

• Non-metals react with oxygen to form non-metal oxide.

Non-metal + Oxygen → Non-metal oxide

C + O₂ → CO₂

• Non-metals do not react with water and acids to evolve hydrogen gas.
• Non-metals can react with salt solution; more reactive elements will displace the less reactive non-metal.

2 NaBr (aq) + Cl₂(aq) → 2NaCl (aq) + Br₂ (aq)

• Non-metals can also react with hydrogen to form hydrides.

H₂(g) + S(l) → H₂S(g)

Reactivity Series

The series in which metals are arranged in the decreasing order of reactivity, it is known as Reactivity Series.

Fig.1. Reactivity Series

Ionic Compounds

Compounds formed due to the transfer of electrons from a metal to a non-metal are known as Ionic Compounds.

Covalent Bond

Bond formed by sharing of electrons between the two atoms. They share their valence electrons to gain stability.

Properties of Ionic Compounds

• They are generally hard and solid.
• They have a high melting and boiling point.
• They are soluble in water but insoluble in inorganic solvents such as ether etc.
• They are conductors of electricity in molten and solution state.

Occurrence of Metals

Elements or compounds which occur naturally in earth crust are known as Minerals. Minerals from which pure metals can be extracted are known as Mineral Ores.

Extraction of pure metals from its ores/steps for extraction of metals from its ore

• The first step is enrichment of the ore.
• Second step includes extraction of metals
• Third steps involve refining of metal

Gangue – Ores contain different impurities in it such as sand, soil etc. These impurities are known as Gangue.

Extracting Metals which are low in activity series

Metals which are low in activity series are unreactive. The oxides of such metals can be reduced to metals by heating alone. For Example, Cinnabar (HgS)

Extracting Metals in the middle of the Activity Series

These metals are moderately reactive. They exists as sulphides or carbonates in nature. Before reduction, metal sulphides and carbonates must be converted into metal oxides. Sulphide ores are converted into oxides by heating strongly in presence of excess air, this is known as Roasting. Carbonate ores are converted into oxides by heating in limited air. This is known as Calcination.

Roasting

Calcination

Reduction-metal oxides can be reduced to metals using reducing agent such as such as Carbon.

Extracting metals towards the top of the activity series

The metals are highly reactive. They cannot be obtained by heating. For Example, Sodium, magnesium and calcium are obtained by the electrolysis of their molten chlorides.

At cathode  Na⁺ + e^– → Na

At anode   2Cl^– → Cl2 + 2e^–

Refining of Metals

Refining of impure metal is done using electrolytic refining. Impure copper is used as anode and strip of pure copper is used as Cathode. Acidified copper sulphate is used as electrolyte. When electric current is passed through this, impure metal from the anode gets deposited in the electrolyte solution, whereas pure metal from the electrolyte is deposited at cathode.

Deposition of insoluble residue formed from the dissolution of anode during commercial electrolysis.

Electrolytic refining

Corrosion

Metals when exposed to moist air for a long period of time, they become corroded. This is known as Corrosion. For Example, Silver reacts with moist air and becomes black in colour due to silver sulphide coating.

Iron + oxygen → Iron (III) oxide

Fe + O­ 2 → Fe2O3

Prevention of Corrosion

• Rusting of iron can be prevented by oiling, galvanising, painting, greasing etc.
• To protect steel and iron from rusting, a thin layer of zinc is coated on them, this is known as Galvanization.

Alloy

Mixture of two or more metals or metal and non-metal is known as Alloy. For Example,

• Brass is an alloy of copper and zinc.
• Bronze in an alloy of copper and tin.
• Solder is an alloy of lead and tin.
• Amalgam is one metal that is mercury.