Question

If the seventh period is completed, the atomic number of the last element would be:

• A. $118$
• B. $112$
• C. $107$
• D. $120$

Answer 1

The correct option is A $118$

As the seventh period will be completely filled its electronic configuration must be in the manner of noble gas configuration i.e., $n{s}^2,n{p}^6$ because the last element in every period is a noble gas element.

Hence, the electronic configuration of the last element of the seventh period is (Rn) $5f^{14}6d^{10}7s^{2}7p^6$ as the electronic configuration contains $118$ electrons.

The last element in the seventh period will have the atomic number $118$.