# Which subatomic particle plays the greatest part in determining the properties of an element?

The identity of the element is determined by $Z \text{, the Atomic Number}$, so..........
Since $Z$ is EXPLICITLY determined by the number of protons, massive, positively charged particles, present in the element's nucleus, the proton must be the greatest determinant. Of course, it is the electrons that actually do the chemistry, but $Z$ defines the element.