Atomic number of Calcium is 20 and its electronic configuration is 2, 8, 8, 2. To see the resemblance with Calcium, first we have to check the Electronic Configuration of respective elements.

From above, it is clear, elements with atomic number 12 and 38 has same electronic configuration of valence shell as that of Calcium, and therefore, will have physical and chemical properties resembling calcium.

(a) Group 17 belongs to halogen family and thus, A is non-metal.
(b) C is less reactive than A because the reactivity of non-metal decreases from top to bottom.
(c) Since the size decreaes across a period on moving from left to right, the size of C is smaller than B because B and C belong to the same period.
(d) A forms anion because C is non-metals for anion (negative ion).

(a) The properties of all elements in the boron family
      (i) All the elements show valency of 3.
(b) The properties of  all the elements in halogen family
    (i) All the elements possess seven electrons in the valence shell.

(a) Neon (Ne), Neon has two completely filled shells with 2 electrons in K shell and 8 electrons in L shell.
(b) Magnesium (Mg).
(c) Silicon (Si). Silicon has a total of three shells. K shell has 2 electrons, L has 8 and M i.e. valence shell has 4 electrons.
(d) Boron (B). It has a two shells, with 3 electrons in its L i.e. valence shell and 2 electrons in K shell
(e) Carbon (C) has electronic configuration of 2 electrons in K shell and 4 electrons in L shell. Clearly, it has twice as many electrons in its second shell as in its first shell.