Question

elements in the same group of the periodic table have the same:
o number of protons
o number of neutrons
o number of valence electrons
o atomic mass

Explanation:

Elements in the same group of the periodic table share similar chemical properties due to having the same number of valence electrons. The number of protons defines the element itself and varies across a group. Neutron numbers can vary even within the same element (isotopes). Atomic mass also changes down a group as more protons and neutrons are added.

Answer:

Number of valence electrons