Radioactive elements

Inside an atom there are three kinds of particle: protons, nuetrons and electrons.The nucleus, the tiny core of the atom,contains protons and neutrons.The region beyond the nusleus contains(negatively charged)electrons that balance out the charge of the protons.There are roughly as many protons as neutrons,which is why the atomic weight is about(but not exacly)twice the atomic number.because like charges repel each other,there is always a force trying to push the protons apart.Provided there are not too many protons in the nucleus, other forces can hold the protons together.but if the ratio of protons to neutrons is not within certain limits,protons may not be held firmly together,and they form an unstable nucleus.This is what makes isotopes of some elements radioactive.
For example, carbon,the element found in all living things has the chemical symbol C.The normal form (isotope)has an atomic weigh of 12and is written as carbon-12,but the radioactive(isotope)version has two extra neutrons, so the symbol is carbon-14.
As we shall see, the radioactive form behaves chemically just like the non-radioactive form, although one will never change into the other.There are Three types of radioactivity, each with different radiation type.