Isotope of an element differ in their

The ansewer is Atomic masses

Isotopes of an element have a same atomic number but differ in their atomic masses. Atomic number indicates a number of protons and atomic mass indicate the number of neutrons plus proton present in the atom. So atoms with the same number of protons but different number of neutrons are termed as isotopes.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.