Consider the three elements P, Q and R having atomic numbers 8,12 and 18 respectively: 
(i) Which of these elements can combine together to form a compound?
(ii) Show the formation of the above compound using electron dot structure.
(iii) State the period and the group to which element Q belongs
(iv) What is formed when Q reacts with boiling water?
(v) Name two other members that belong to the same group as R.