Question

An ion X^2- contains 10 electrons and 14 neutrons. What are the atomic no. and mass no. of the element X? Name the element.

Answer 1

Ion x^2- has

e- = 10
n = 14
p+ = ??


Now since its anion, it has 2 more electrons. So, original number of electrons = 10 - 2 = 8

Original number of electrons = number of protons

=> p+ = 8

So, atomic number = number of protons = 8

Mass number = p + n = 8 + 14 = 22

Element with atomic number 8 is, Oxygen, but its mass number is 14, so the element is isotope of Oxygen

Answer :- O22 is the element.