1. i. B. 3
ii. A. 2
iii. D. XO2
iv. C. P2O
v. C. M2(SO4)3
2. (a) (i) Atomicity of an element is the number of atoms present in one molecule of of an element eg. the atomicity of a molecule of N2 is 2.
(ii) A radical is a group of atoms that act as one atom but does not exist independently.
(iii) Valency is the combining capacity of an atom.
(b) (i) A molecule is a group of two or more atoms chemically bonded together, while an atom is the smallest particle of an element that can take part in a chemical reaction.
(ii) Similar kinds of atoms: O2, N2, H2 Different kinds of atoms: H2O, CO2, CH4
(c) (i) H2SO4: 2 hydrogen, 1 sulphur, 4 oxygen
(ii) FeSO4: 1 iron, 1 sulphur, 4 oxygen
(iii) Pb(NO3)2: 1 lead, 2 nitrogen, 6 oxygen
(d) (i) H2O: 2 elements, which are hydrogen and oxygen
(ii) CO2: 2 elements which are carbon and oxygen
(iii) (NH4)3PO4: 4 elements which are nitrogen, hydrogen, phosphorus and oxygen
3. (a) (i) K2SO4
(ii) CaCl2
(iii) Al(NO3)3
(iv) (NH4)2SO4
(b) (i) Calcium sulphate
(ii) Copper(II) nitrate
(iii) Copper(II) chloride