Question

Write the electronic configuration of the element with atomic number 17. Indicate the valency of the element.

Answer 1

Atomic number is 17
So, the no. of protons and no. of electrons is 17.

Electronic configuration is

$\begin{array}{ccc}\underset{2}{\mathrm{K}}& \underset{8}{\mathrm{L}}& \underset{7}{\mathrm{M}}\end{array}$

Here, the outermost orbit has 7 electrons. In order to make it 8, the element will have to gain 1 electron. So, the valency of the element is 1.