Question

An ion x2_ contains 10 electron and 8 neutron .what are the atomic number and mass number of element x

Answer 1

Atomic number = 10 - 2 =8
Atomic mass = protons + neutrons
As protons are equal to electrons
Atomic mass = 8 + 8
= 16

Answer 2

The ion x2- has 10 electrons means, the element x has no. of electrons = 10-2 = 8

Now, atomic number =no of protons= no of electrons = 8

and mass number = no of neutrons + no of protons =8+8= 16

Hope this helps..