Carbon atoms can be identified based on the # of which subatomic particles

protons and neutrons.

The nucleus is made up of 3 subatomic particles that are protons,neutrons and electrons.  

General notation of an element is

where, X is the Element, A is the Atomic Mass and Z is the Atomic Number

If we know the number of protons we can easily find out the atomic number of any element because Atomic Number = Number of protons in an element.

And in addition if we know the number of neutrons we can easily find out the atomic mass of an element because

Atomic Mass = (Number of protons) + (Number of neutrons)

If we get to know the atomic number and atomic mass, we can easily tell what element is it by looking from the periodic table.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates