The___ of an element is the number of element.*
__ of an atom of that
atomic mass, electrons in the nucleus
mass number, neutrons in the nucleus
mass number, protons plus neutrons in the outermost energy level
atomic number, protons in the nucleus

atomic mass, neutrons in the nucleus

Explanation: because I remember from when I took honors chemistry last year we learned about this and it’s called the atomic mass when looking at an atom and the neutrons in the nucleus are effected by it.

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.