Protons, Neutrons, and Electrons:

*Protons and Neutrons have a mass of 1AMU.

*Electrons hardly have any mass -> .000525AMU.

Atomic # = # of Protons

• The # of protons identifies an atom.

• The Mass of an atom is the sum of all protons and neutrons.

Atomic Mass = P + N

We round the atomic mass to the nearest whole #, 4.

Since we already determined that Helium has 2 protons that means:

4 (mass) = 2 P and(+) ? Neutrons

2 Plus what equals 4?

2!! The amount of Neutrons in a Helium atom is 2.