Ncert Exercises & Solutions

The elements with atomic numbers 35, 53, and 85 are:

1.	Noble gases	2.	Halogens
3.	Heavy metals	4.	Light metals

HINT: The group contains most electronegative element.

Explanation:

Each period ends with a noble gas. The atomic number of noble gases (i.e., group 18 elements) are 2, 10, 18, 36, 54 and 86.

Therefore, elements with atomic numbers 35(36-1), 53(54-1) and 85(86-1), lie in a group before noble gases, i.e., halogens (group 17) elements.

Thus, the elements with atomic number 35, 53, and 85 all belong to halogens.