Question

How many neutrons are present in 21Ne?

Answer 1

The number of neutrons present : 11

Further explanation

Given

²¹Ne

Required

Number of neutrons

Solution

In the following element notation,

$\large {{{A} \atop {Z}} \right X}$

X = symbol of element

A = mass number

   = number of protons + number of neutrons

Z = atomic number

   = number of protons = number of electrons, on neutral elements

So the symbol above shows the mass number Ne: 21

Ne itself has an atomic number of 10, so the number of neutrons :

number of neutrons  = mass number - atomic number

number of neutrons  = 21 - 10

number of neutrons  = 11