# Two atoms have the same number of protons but different numbers of neutrons. What can you conclude about these two atoms?

##### 1 Answer
Dec 6, 2015

That they are isotopes, i.e. the same element, but different atomic masses.

#### Explanation:

The number of nuclear protons gives $Z$, the atomic number. The atomic number defines the identity of the element: $Z$ = 6, $C$; $Z$ = 27, $C o$; $Z$ = 47, $A g$.

Of course while there may be the same number of nuclear protons, the nucleus may contain different numbers of neutrons; these give rise to different isotopes; same element, and same chemistry, but different atomic mass. Most elements have a number of isotopes. The quoted atomic mass that appear on the Periodic Table are the weighted average of the isotopes.