Which of the following statement is not correct?
1
Isotopes of an element have same atomic number but different mass numbers
2
The electronic configuration of isotopes of an element is different
3
The atoms which have the same mass number but different atomic numbers are called isobars
4
Two nuclei A and B are isotonic with mass numbers 15 and 16 respectively. If A contains 7 protons, then the number of protons in B would be 8