What are the similarities and dissimilarities be­tween isotopes of same species? Give example with reasons.

Isotopes:

1. The atoms of the same element having the same atomic number but different mass numbers are known as isotopes. i.e. same number of protons but different numbers of neutrons.
2. Similarity between isotopes of same species is that they have same number of protons. Thus, they have same atomic numbers.
3. Dissimilarity between isotopes of same species is that they have different number of neutrons. Thus, they have different mass numbers.

Example: Isotopes of hydrogen:

Hydrogen has three isotopes: Protium, Deuterium and Tritium

Protium:

1. It has $1$ proton. Thus, the atomic number is $1$.
2. It has $0$ neutrons. Thus, the mass number is $1$.
3. It is represented as ${}_1{}^1\mathrm{H}$.

Deuterium:

1. It has $1$ proton. Thus, the atomic number is $1$.
2. It has $1$ neutrons. Thus, the mass number is $2$.
3. It is represented as ${}_1{}^2\mathrm{H}$.

Tritium:

1. It has $1$ proton. Thus, the atomic number is $1$.
2. It has $2$ neutrons. Thus, the mass number is $3$.
3. It is represented as ${}_1{}^3\mathrm{H}$.

Thus, the isotopes of Hydrogen are ${}_1{}^1\mathrm{H}$, ${}_1{}^2\mathrm{H}$ and ${}_1{}^3\mathrm{H}$.