3. Draw electron diagrams (showing electrons in the outermost shell only) for the following compounds. (a) Calcium chloride, CaCl2 (b) Lithium sulphide. Li2S

(4 marks)

4. Hydrogen reacts with oxygen to form a compound X. (a) Name the compound formed between hydrogen and oxygen. ____________________________________________________________________________________ (b) Write the molecular formula of the compound X. ____________________________________________________________________________________ (c) Draw the electron diagram of compound X.

HPHS4068/ Ex 1/ Ch 1-2/ P.11

(d) Write down the number of bond pairs and lone pairs on the oxygen atom in compound X. Number of bond pairs = __________ Number of lone pairs = ___________ . Elements P, Q, R and S (letters only, not chemical symbols) have atomic numbers of 11, 6, 17 and 10 respectively.

5(a) Write the formula of the compound (if any) you would expect to form between the following elements. (i) P and S (ii) P and R (iii) Q and R (b) For the compound formed in (a)(iii), (i) Draw the electron diagram of a molecule of this compound.

(ii) Name the attractive force between the molecules in this compound. __________________________________________________________________________________ (5 marks)