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

Proton

Explanation:

We know that atomic number is equal to proton number.

If we know the proton number then we  can determine the atomic number  and number of electrons.

Because number of protons=Number of electrons.

If we know that atomic number then we can determine the electronic configuration.

We can determine valency of an element by determining outer  electronic configuration.

If we know electronic configuration then we can know that the element from which period and group belongs.

Hence, the proton particle plays the greatest part in determining the properties of an element.

that's what i got you can count the number of atoms

the objects have the same charge is correct.

nathan lee