Answers

2016-07-09T15:37:44+08:00
Proton determines the atomic number of your element/isotope. And the mass of your element is the sum of Neutron and Proton. 

11 + 13 = 24

The number of proton (11) determine what will be your element/isotope, therefore your isotope notation for this given values will be 

24
    Na
 11
 
1 5 1