Question

The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belong to the same group?
(a) A and B
(b) B and D
(c) A and C
(d) D and E

NCERT Class X
Science - Exemplar Problems

Chapter_Periodic Classification of Elements

Answer 1

Option (c) is correct .

Answer 2

concept
element will be on same group when they have same valence electron
for A ---2,7
B-----2,8,1
C------2,8,7
D-----2,8,2
E-----2,8,3
answer is element A and C,both have 7 valence electron