Which particles contribute to the atomic number and why ??

the number of protons in the nucleus that are found in an atom is what determines an element's atomic number.why you may ask and thats because Protons contribute to the mass of an atom.(along with neutrons but they dont have a charge)but protons provide a positive charge to the nucleus.  

Explanation:

because the atom is electrically neutral, the number of electrons must equal the number of protons.

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