Question

An element has an atomic number of 107. What is its electronic configuration and what will be its group number?

• A. $\left[Rn\right]5f^{14}6d^{1}7s^{2}7p^4$, group 3
• B. $\left[Rn\right]5f^{14}6d^{5}7s^2$, group 7
• C. $\left[Rn\right]5f^{14}7s^{2}7p^5$, group 7
• D. $\left[Rn\right]5f^{14}6d^{2}7s^{2}7p^3$, group 15

Answer 1

The correct option is B $\left[Rn\right]5f^{14}6d^{5}7s^2$, group 7

In accordance with Aufbau principle, the most stable electronic configuration is (b) and its group number is 7.

If you look at option (a), 7p electrons are filled without finishing 6d.
If you look at option (b), 7p electrons are filled without even starting to fill the 6d
Figure out option (d) on your own.