The Secret to Understanding Isotopes

This article is about isotopes (in chemistry), how an isotope is defined, and possible applications of them. First of all though, to understand the term isotope it's important to know what atomic number and mass number is. Once we know those to terms, isotopes are pretty simple terms to grasp.

Every element has been given a number depending on how many neutrons and protons there are in its nucleus. If an element has two protons and two neutrons, its mass number will be the total of those two, which is four. In chemistry mass number is often written with an A, and the number of protons is written with a Z. This means that you will get the formula A = Z + number of neutrons.

You could look at it in a different perspective; if you wanted the number of neutrons present in an atom, you would subtract the number of protons (Z) from the mass number (A), and then you would have it.

The number of protons is given its own name in chemistry; we call it the atomic number of an atom. There's no hocus pocus to this, atomic number is the number of protons, and mass number is the number of neutrons added.

Sometimes though, an atom will be changed a bit. The number of protons stays the same (if the number of protons is not the same, then it's not the same element), but the number of neutrons change. This gives the atoms a different mass number, but it will still be the same element.

In fact, anywhere you see an atom with a particular number of protons and neutrons - it will always be the same element, it's just a different isotope of that element. The isotope will have almost identical chemical behavior as the original element, because they still have the same number of electrons.

In nature most elements are found as a mixture of isotopes. To write the name of an isotope you put the name of the element, followed by a "-", and then it's mass number. Putting this to the test on the three carbon isotopes that occur in nature we get carbon-12 (6 protons, 6 neutrons), carbon-13 (6 protons, 7 neutrons) and carbon-14 (6 protons, 8 neutrons). The important thing to remember is that the number of protons stays the same, and the only thing that changes is the neutrons.

Some isotopes can be very unstable, and the nucleus begins to decay as a result of this. As the nucleus decays it gives off energy, and this is the basis for radioactive elements, where isotopes play a huge role.

The most important things to remember from this chemistry help article are the terms atomic mass, atomic number, and isotopes.