1. All atoms of the same element have the same
O mass
O number of neutrons
O mass numbers
number of protons

All atoms of the same element have the same number of protons

Explanation:

All atoms of the same element have the same number of protons. The atoms are formed by protons, neutrons (both located in the nucleus) and electrons located on the outside. The number Z characterizes each element (corresponds to the number of protons located in the nucleus, which coincides with the number of electrons). The number A corresponds to the sum of protons and neutrons of an element (it varies in isotopes, since the number of neutrons varies).

a