Question

One mole of an element contains $4.2\times {10}^{24}$ electrons. What is the atomic number of the element?

Answer 1

According to the problem

Atomic Number =$x$

Electron is one mole=$a\times 6.023\times {10}^{23}$

$x=\frac{4.2\times 1024}{6.023\times {10}^{23}}$

$x=7$

Hence the atomic number is $7$.