Question

Five atoms are labelled as $\mathrm{V}$ to $\mathrm{Z}$.

Atoms	Mass Number	Atomic number
$\mathrm{V}$	$40$	$20$
$\mathrm{W}$	$19$	$9$
$\mathrm{X}$	$7$	$3$
$\mathrm{Y}$	$16$	$8$
$\mathrm{Z}$	$14$	$7$

Which of these atoms:

(i) contains 7 protons

(ii) has electronic configuration 2, 7?

Answer 1

(i)

Atomic number: The total number of protons present in the nucleus of an atom gives the atomic number of the atom.

Number of protons = Atomic number

Therefore, an atom containing 7 protons is

(ii)

An atom containing an electronic configuration $2,7$will contain total $9$ electrons.

Since in an atom, the number of electrons = number of protons = atomic number

The atomic number $9$ for $\mathrm{W}$ atom.

Therefore, atom having electronic configuration $2,7$is $\mathrm{W}$.