Basically there are three subatomic particles in all atoms of elements including protons, neutrons and electrons. All atoms of the elements have same number of electrons, and protons. On the other hand, isotopes of same elements can have different number of neutrons. This is the only atomic difference between the isotopes of the same element that number of neutrons are not same.
For example, there are three isotopes of hydrogen element which includes protium, deuterium and tritium. Protium atom are the normal hydrogen atoms which have only one proton and no neutron. That is why it is denoted as 1H. Deuterium is the atom of hydrogen which has one proton and one neutron and is written as 2H. Tritium on the other hand, has two neutrons and one proton and can be written as 3H. This shows that the only difference in the isotopes is that of the number of neutrons.
For example, there are three isotopes of hydrogen element which includes protium, deuterium and tritium. Protium atom are the normal hydrogen atoms which have only one proton and no neutron. That is why it is denoted as 1H. Deuterium is the atom of hydrogen which has one proton and one neutron and is written as 2H. Tritium on the other hand, has two neutrons and one proton and can be written as 3H. This shows that the only difference in the isotopes is that of the number of neutrons.
