Question

Five elements A,B,C,D and E have atomic number 2,9,11,12 and 20 respectively:
1) Which pair of elements belongs to the same group?
2) Which pair of elements belongs to the same period?

Answer 1

1) 12, 20 belongs to same group
2) 11 , 12 belongs to same period

Answer 2

ans.1. element D and E because their valence electron are same that is 2
D (2,8,2)
E (2,8,8,2)
ans.2. element C and D because they both contain same no. of shell that is 3 no. of shell
C (2,8,1). 3 shells
D(2,8,2). 3 shells

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