Question

Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period? [NCERT Exemplar Problems]
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E

Answer 1

Answer:

b) B,C,D.

Explanation:

2 helium, 3 lithium, 7nitrogen, 10 neon 30 zinc.

2.8

Elements b , c , d belongs to the same period because the no. of valence shells are all 2.