Notes of ch 3 metals and non metals - Class 10 PDF Download

Examples:

(i) 2Na 2H2O → 2NaOH H2  Heat

(ii) Ca 2H2O → Ca(OH)2  H2

(iii) Mg 2H2O → Mg(OH)2  H2

(iv) 2Al 3H2O → Al2O3  3H2

(v) 3Fe 4H2O → Fe3O4  4H2

• Reaction of metals with acids (Dilute)

→ Metal Dilute acid → Salt H2
→ Cu, Ag, Hg do not react with dil. acids.

Examples:

(i) Fe 2HCl → FeCl2  H2
(ii) Mg 2HCl → MgCl2 H2
(iii) Zn 2HCl → ZnCl2  H2

(iv) 2Al 6HCl → 2AlCl3  3H2

• Reaction of Metals with Solutions of other Metal Salts 

→ Metal A Salt solution B → Salt solution A Metal B
→ Reactive metals can displace less reactive metals from their compounds in solution form.

Fe CuSO4→ FeSO4  Cu

Reactivity Series

The reactivity series is a list of metals arranged in the order of their decreasing activities.

• Reaction of Metals with Non-metals

→ Reactivity of elements is the tendency to attain a completely filled valence shell.
→ Atoms of the metals lose electrons from their valence shell to form cation. Atom of the non-metals gain electrons in the valence shell to form anion.

E.g.: Formation of NaCl
  Na   →   Na   e-
2, 8, 1         2, 8

Sodium cation
Cl e-   →   Cl-
2, 8, 7        2, 8, 8

Chloride anion

Ionic compounds

The compounds formed by the transfer of electrons from a metal to a non-metal are called ionic compounds or electrovalent compounds.

• Properties of Ionic Compounds

(i) Physical nature: They are solid and hard, generally brittle.

(ii) Melting and Boiling Point: They have high melting and boiling point.

(iii) Solubility : Generally soluble in water and insoluble in solvents such as kerosene, petrol etc.

(iv) Conduction of electricity : Ionic compounds conduct electricity in molten and solution form but not in solid state.

• Occurrence of Metals

(i) Minerals: The elements or compounds which occur naturally in the earth’s crust are called minerals.

(ii) Ores: Minerals that contain very high percentage of particular metal and the metal can be profitably extracted from it, such minerals are called ores.

Extraction of Metals from Ores

Step 1. Enrichment of ores.
Step 2. Extraction of metals.
Step 3. Refining of metals.  

Steps Involved in Extraction of Metals from Ores

Gangue → Roasting → Calcination → Reduction

• Important terms

(a) Gangue : Ores are usually contaminated with large amount of impurities such as soil, sand etc. called gangue.

(b) Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is called roasting.
2ZnS 3O2 →(Heast) 2ZnO 2SO2

(c) Calcination : The carbonate ores are changed into oxides by heating strongly in limited air. This process is called calcination.
ZnCO3 →(Heat) ZnO CO2

(d) Reduction : Metal oxides are reduced to corresponding metals by using reducing agent like carbon.
ZnO C → Zn CO

• Refining of metals

The most widely used method for refining impure metal is electrolytic refining.

(i) Anode : Impure copper

(ii) Cathode : Strip of pure copper

(iii) Electrolyte : Solution of acidified copper sulphate

→ On passing the current through electrolyte, the impure metal from anode dissolves into the electrolyte.

→ An equivalent amount of pure metal from the electrolyte is deposited at the cathode.

→ The insoluble impurities settle down at the bottom of the anode and is called anode mud.

Corrosion

The surface of some metals get corroded when they are exposed to moist air for a long period of time. This is called corrosion.

Examples:

(i) Silver becomes black when exposed to air as it reacts with air to form a coating of silver sulphide.

(ii) Copper reacts with moist carbon dioxide in the air and gains a green coat of copper carbonate.

(iii) Iron when exposed to moist air acquires a coating of a brown flaky substance called rust.

• Prevention of Corrosion

→The rusting of iron can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing or making alloys.

→ Galvanization : It is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.

→ Alloy : An alloy is a homogeneous mixture of two or more metals or a metal and a non- metal.

→ Examples of alloy:

(i) Iron : Mixed with small amount of carbon becomes hard and strong.
(ii) Steel : Iron Nickel and chromium
(iii) Brass : Copper Zinc
(iv) Bronze : Copper Tin (Sn)
(v) Solder : Lead tin
(vi) Amalgam : If one of the metal is mercury (Hg).