This question refers to the elements of the periodic table with atomic numbers 3 to 18.
(a) (i) Which of them are noble gases?
(ii) Which of them are halogens?
(iii) Which of them are akali metals?
(iv) Which are the elements with valency 4?
(b) An element with atomic no. 3 combines with another element with atomic number 17; what would be the formula of the compound?
(c) What is the electronic configuration of an element with atomic number 10?
(a) (i) Elements of 18 groups are noble gases. So Neon (Ne) with atomic number 10 and Argon (Ar) with atomic number 18 are the noble gases because these have complete octet.
(ii) Elements of 17 group are halogens. So Fluorine (F) with atomic number 9 and Chlorine (Cl) with atomic number 17 are halogens.
(iii) Elements of 1 group are alkali metals except hydrogen (H). So Lithium (Li) with atomic number 3 and Sodium (Na) with atomic number 11 are alkali metals.
(iv) Elements with valency 4 are elements of group 14. So Carbon (C) with atomic number 6 and Silicon (Si) with atomic number 14 are elements with valency 4.
(b) Element with atomic number 3 is Li which has 1 valence electron and element with atomic number 17 is Cl has 7 valence electrons. Element with atomic number 17 wants one electron to complete its octet. So the formula will be LiCl.
(c) The electronic configuration of element with atomic number 10 is
10Ne- 2, 8