(1)- june 2000- when any metal reacts with steam, the products are always the metal hydroxide and hydrogen gas. So , eliminate answers C and D. From A and B, only iron is more reactive than Hydrogen thus it's the only metal here that can displace hydrogen from steam. Copper is less reactive than hydrogen so it won't react with steam. The correct answer is B
(2)-june 2009- if S has 18 protons then it has 18 electrons so it's arrangement will be 2,8,8 . If T is the next element then it should have 19 protons so 19 electrons making its arrangement this way 2,8,8,1. So it is clear than T will have one more shell than S so the answer must be B.
(3)- june 2010-X cannot gain an electron and remain an atom. So both A and B are wrong ( when it gains an e it will be X-)
So, out of C and D, only D makes sense.Because Isotopes have the same proton nbr but diff. neutron nbr. When we move across a period of the periodic table, each successive atom gains a proton. So the correct answer is D
