Calculate the atomic number of an element whose atomic nucleus has mass number 23 and neutron number 12. What is the symbol of the element ?

Explanation

We know that :
Mass number = Atomic number + No. of neutrons
So, 23 = Atomic number + 12
And, Atomic number = 23 - 12
= 11
The element having atomic number 11 is sodium and its symbol is Na. If, however, we indicate the atomic number and mass number also, then the symbol becomes `._(11)^(23)Na`, where 11 is the atomic number and 23 is the mass number.