"A radical is an atom of an element or a group of atoms of different elements that behaves as a single unit with a positive or negative charge on it" Radicals are of two types : (1) Basic radicals: They have a positive charge and are also called cations. All metallic ions and ammonium ions are basic radicals. (ii) Acid radicals: They have a negative charge and are also called anions. Most of the non-metallic ions and groups of non-metallic atoms with a negative charge is acid radicals.

Balance the following equation: Cu + HNO 3 → Cu NO 3 2 + H 2 O + NO 2

The representation of a chemical reaction in the form of substances is known as a chemical equation. The equation in which the number of atoms of all the molecules is equal on both sides of the equation is known as a balanced chemical equation. When copper reacts with concentrated nitric acid, reddish coloured poisonous nitrogen dioxide gas is formed. Cu + 4 HNO 3 → Cu NO 3 2 + 2 H 2 O + 2 NO 2

Balance the following equation. KMnO 4 + HCl → KCl + H 2 O + MnCl 2 + Cl 2

A balanced equation is an equation for a chemical reaction in which the total number of the reactants and the products should be same. 2 KMnO 4 + 16 HCl → 2 KCl + 2 MnCl 2 + 8 H 2 O + 5 Cl 2 . The 2 moles of potassium permanganate reacts with the 16 moles of HCl gives 2 moles of KCl .

Balance the following equation: Al 2 O 3 + H 2 SO 4 → Al 2 SO 4 3 + H 2 O

When the number of atoms of reactants is equal to the number of atoms of the products, the reaction is called a balanced chemical equation. Aluminium oxide reacts with sulphuric acid to form salt aluminium sulphate and water. Al 2 O 3 + 3 H 2 SO 4 → Al 2 SO 4 3 + 3 H 2 O

Balance the following equation: Pb ( NO 3 ) 2 → PbO + NO 2 + O 2

A chemical equation in which the number of atoms of each element is equal on both sides of the equation is known as a balanced chemical equation. The balanced chemical equation for the given reaction is: 2 Pb ( NO 3 ) 2 → 2 PbO + 4 NO 2 + O 2 A balanced chemical equation always follows the law of conservation of mass.