Answer
These atoms each have a different number of neutrons. The first atom has 6 neutrons, the middle atom has 7 neutrons, and the right atom has 8 neutrons. These atoms are isotopes. They are all carbon, but they have different masses based on their number of neutrons.
Work Step by Step
These three atoms are isotopes. This means they have the same number of protons, and are therefore the same element. However, they have different numbers of neutrons. Neutrons do not affect the identity of the element, but they do affect the weight of the atom. A carbon isotope with 8 neutrons is heavier than a carbon isotope with 7 or 6 neutrons.
