This question refers to elements of the periodic table with atomic numbers from 3 to 18. In the table below, some elements are shown by letters, even though the letters are not the usual symbols of the elements.
| 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| A | B | C | D | E | F | G | H |
| 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
| I | J | K | L | M | N | O | P |
(a) Which of these is
(i) a noble gas
(ii) a halogen
(iii) an alkali metal
(iv) an element with valency 4
(b) If A combines with F, what would be the formula of the resulting compound?
(c) What is the electronic configuration of G?
(a) (i) H and P are noble gases, as they are in group zero and have their octet complete.
(ii) G and O are halogens, as they are in group VIIA and have 7 valence electrons.
(iii) A and I are alkali metals, as they are in group IA and have 1 valence electron.
(iv) D and L have valency 4, as they are in group IVA and have 4 valence electrons.
(b) Valency of A [2, 1] is +1, so it tries to donate an electron and attain a stable state.
Valency of F [2, 6] is -2, so it tries to gain two electrons and attain a stable state. Hence, one F atom takes electron from two A atoms. Therefore, the formula of their compound will be A2F
(c) Electronic configuration of G is [2, 7] as its atomic number is 9.