Question
Chemistry Question on Classification of elements & periodicity in properties
Which of the following pairs of atomic numbers represents elements belonging to the same group?
A
11 and 20
B
12 and 30
C
13 and 31
D
14 and 33
Answer
13 and 31
Explanation
Solution
Element with At. No. 13 is in third period and group 13. The next element below this will have At. No. 13 + 18 = 31