Protons have a positive electric charge and a mass of about 10 -27 grams.
Neutrons have no charge and weigh about the same as a proton.
An element consists of all atoms a particular type. For example, carbon is an element, and so is hydrogen. Isotopes Elements can have a variable number of neutrons in their nucleus. Radioactive Isotopes Nuclei with too few or too many neutrons are unstable and will decay with a characteristic timescale called the half life . The result of the decay is a different element.