SEP Develop Models Each helium atom has two protons. Sketch models of helium-3 and helium-4, which have approximate masses of 3 amu
and 4 amu, respectively. Label and differentiate protons, neutrons, and
electrons in your models?

Protons and neutrons are located in the nucleus of the atom while the electrons move in the trajectory of the shell

Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.  

So Isotopes are elements that have the same Atomic Number (Proton)  

Isotopes of Helium : helium-3 and helium-4

protons = 2

electrons=protons=2

neutron=mass number-atomic number=3-2=1

protons = 2

electrons=protons=2

neutron=mass number-atomic number=3-2=1

protons = 2

electrons=protons=2

neutron=mass number-atomic number=4-2=2

Protons and neutron in the nucleus, electrons in the shell