proton

1st shell

2nd shell

neutron

nucleus

electron

Six is the

of carbon. It equals the total number of

in the atom's nucleus.

electrons

isotope

atomic mass

atomic number

protons

neutrons

This is the

of carbon. It equals the total mass of all

and

in the atom's nucleus.

electrons

isotope

atomic mass

atomic number

protons

neutrons

Occasionally, atoms will have more or fewer neutrons than

. This

is called a(n)

. Carbon-13 and carbon-14 are examples.

electrons

isotope

atomic mass

atomic number

protons

neutrons