Question

The atomic numbers of elements A B C D E ARE 7 10 12 4 9 RESPECTIVELY WHICH ELEMENT BELONGS TO THIRD PERIOD OF PERIODIC TABLE

Answer 1

Answer:

Element With atomic number 12/ Element C.

Explanation:

Do Electronic configuration of each element:

Element Number-K-L-M-N

7 - 2-5

10- 2-8

12 - 2-8-2

4 - 2-2

9 - 2-7

As you can see the element with atomic no. 12 has electronic configuration of 3 shells. It means it belongs to period 3rd. On other hand Element with 7 have 2 Shells meaning that it belongs to period 2.