Two atoms will always have the same atomic number if they have the same a. mass number
b. number of protons
c. number of neutrons
d. number of nucleons

b. number of protons

Explanation:

The definition of the atomic number is the number of protons.

It is possible for two atoms to have the same mass number but a different number of protons (for example one atom with 23 protons and 25 neutrons, and one atom with 24 protons and 24 neutrons). This is because the mass number is equal to the sum of the number of protons and neutrons.

what are the two models

explanation:

pie chart because it is in percents ( % )