CBSE Class 10 Science 2020 · Paper 31/1/1 · Question 26(a)

Periodic Classification of Elements 5 marks Medium

The position of certain elements in the Modern Periodic Table are shown below. Using the above table answer the following questions giving reasons in each case :

(i)Which element will form only covalent compounds?
(ii)Which element is a non-metal with valency 2 ?
(iii)Which element is a metal with valency 2 ?
(iv)Out of H, C and F which has largest atomic size?
(v)To which family does H, C and F belong?

Positions of certain elements in the Modern Periodic Table
Period ↓ / Group →	1	2	13	14	16	18
1	G					H
2	A		I		B	C
3		D		E		F

Answer

E forms only covalent compounds, B and D have valency 2, F has the largest size, and H, C and F are noble gases.

(i) E: it is in group 14 and has 4 valence electrons, which it can neither lose nor gain easily, so it shares electrons and forms only covalent compounds. (ii) B: it is in group 16 with 6 valence electrons and needs only 2 more electrons to attain a stable configuration, so it is a non-metal with valency 2. (iii) D: it is in group 2 with 2 valence electrons, which it loses to attain a stable configuration, so it is a metal with valency 2. (iv) F: H, C and F are in the same group (18), and atomic size increases down a group as a new shell is added; F, in period 3, has the most shells and the largest size. (v) H, C and F belong to the family of noble gases (group 18), because their outermost shells are complete.

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CBSE Class 10 Science 2020 · Paper 31/1/1 · Question 26(a)

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