Which is most likely to influence the properties of an element? * -its atomic mass
-its atomic number
-the number of outer electroms
-the number of isotopes

-the number of outer electrons

Explanation:

Outer electrons are referred to as valence electrons and they are typically what determines the property of an elements such as their reactivity.

For eg, Na (sodium) has 1 valence electron and it really wants to give it aways so it can return back to octet rule (having 8 electrons in outershell) to become stable. So when you put sodium in water (you can watch videos of it) it literally blows because of high reactivity.

the answer to this question is 3.