Explanation:
It is known that isotopes are the species which have same atomic number but different mass number. Whereas a specie which have different atomic number but same mass number are known as isobars.
For example, an element with mass number 35 is chlorine. And, atomic number of a chlorine atom is 17.
This means in a [tex]^{35}_{17}Cl[/tex] atom there are 17 protons and the number of neutrons will be calculated as follows.
Mass number = no. of protons + no. of neutrons
35 = 17 + no. of neutrons
No. of neutrons = 35 - 17
= 18
Hence, we can conclude that the isotope symbol with mass numbers of 35 is [tex]^{35}_{17}Cl[/tex].
