Observe: Turn on Show element symbol and Element notation. Three numbers surround the element symbol: the mass number (A), electrical charge (no number is displayed if the atom is neutral), and the atomic number (Z). Investigate: Watch how the numbers change as you add or remove particles.

Observe: Turn on Show element symbol and Element notation. Three numbers surround the element symbol: the mass number (A), electrical charge (no number is displayed if the atom is neutral), and the atomic number (Z).

Investigate: Watch how the numbers change as you add or remove particles.

Which number is equal to the number of protons in the atom?
How can you calculate the number of neutrons (N) in an atom?
Which particle (proton, neutron, or electron) has a
Positive charge?
Negative charge?
No charge at all?