Question

An element has an atomic number of $19$ and atomic mass of $39$.

(I)How many electrons are there in each atom of the element?

(ii) How are these arranged in the atom?

Answer 1

1. For any neutral atom the number of protons and electrons is same as the atomic number of atom.

Hence, $\mathrm{No}.\mathrm{of}\mathrm{protons}=\mathrm{No}.\mathrm{of}\mathrm{electrons}=\mathrm{Atomic}\mathrm{number}$

No. of protons =$19$

No. of electrons=$19$

Given element is Potassium (K) with Z = 19 and A = 39

2. These electrons are arranged in the atom as $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M}\mathrm{N} \\ 2881 \end{gathered}$$

There are $19$electrons,$2$ electrons go in the $\mathrm{K}$shell, $8$electrons in the $\mathrm{L}$shell, $8$ electrons in the $\mathrm{M}$ shell, and $1$electron in the $\mathrm{N}$ shell.