# Question #48a71

Mar 1, 2014

Isotopes have the same atomic number, while isobars have the same atomic mass.

#### Explanation:

Isotopes are atoms that have same atomic number but different mass numbers.

Isotopes have the same atomic number because the number of protons inside their nuclei remains the same.

They have different mass numbers because they have different numbers of neutrons.

$\text{_17^35"Cl}$ and $\text{_17^37"Cl}$ are isotopes.

They each have 17 protons in the nucleus, but one isotope has 18 neutrons and the other has 20 neutrons.

Isotopes occur at the same place (Greek isos equal + Greek topos place) in the Periodic Table.

Isobars are atoms that have same mass number (Greek isos equal + Greek baros weight) but different atomic numbers.

Isobars have different atomic numbers because they have different numbers of protons.

They have the same atomic mass because they have just enough neutrons to make the same total of nucleons.

$\text{_32^76"Ge}$ and $\text{_34^76"Se}$ are isobars.

The first nucleus has 32 protons and 44 neutrons. The second has 34 protons and 42 neutrons. Each nucleus has 76 nucleons.

Isobars occur at different places in the Periodic Table.