Chemistry Thursday: The atom!

The periodic table. You see it everywhere, but what the heck does it all mean? Take a look at it for a moment. It's arranged by atomic number, which is the number of protons in an atom's nucleus. Let's meet the atom!

When we look at the periodic table of elements, we're looking at the organization of atoms - carbon, oxygen, helium, uranium and so on. There are three parts of an atom. The proton, the neutron, and the electron.

The proton is found in the nucleus of the atom and is positively charged. Every element has a different number of protons. If it has 1 proton, it's hydrogen. Two protons and you've got helium. Six protons gives us carbon and 16 gives us sulphur. Change the number of protons, you change the element. We have the same number of protons as we do electrons, which leads to a neutrally charged atom.

The neutron is found in the nucleus of the atom and is neutrally charged. Change the number of neutrons, and you have an isotope! Normal, everyday carbon-12 has 6 protons and 6 neutrons - carbon-14 has 6 protons and 8 neutrons, giving us a radioactive isotope. (That's why they use it in carbon dating! It decays at a predictable rate, so we can measure the decay and figure out the age of something!) Carbon will always have 6 protons - that's what makes it carbon - but the number of neutrons can change slightly (in carbon it might be 8, it's never going to be 42!). When you hear about elements like uranium-238 or uranium-235, we're talking about isotopes, which are elements that have the same number of protons but different neutrons.

The electron is found swirling around the nucleus. It's really tiny compared to the proton and neutron, and it carries a negative charge. In a neutral state, an atom will have the same number of electrons as it does proton. There's a ton of interesting stuff out there on locating the electrons on an atom - uncertainty principles and all of that, but for now we're going to go with the basic idea that electrons are found outside the nucleus of an atom on things called orbitals.

Orbitals are represented in this picture by those blue lines, the electrons by the red dots!

When you read the periodic table, look at each element to decode its meaning! This is sodium from the first group or column on the periodic table. It is number 11, which means it has 11 protons and 11 electrons (because they are the same number). It weighs 23.0 grams per mole (which is 6.02 x 10(23) atoms in 23 grams of sodium) and it has that plus sign in the corner. This means that there is one electron swirling around on its outer orbital. (This will become relevant in time.)

If you like the periodic table as much as I do, download this periodic table and play periodic table Scrabble! I can't spell my name (Susan - Sulphur-uranium-sulphur-there's no A on its own!) but I can spell my best friend's husband's name - Cameron (Carbon-Americum-Erbium-Oxygen-Nitrogen) and genius (Germanium-Nitrogen-Iodine-Uranium-Sulphur). My last name is easy to create - it's just Ni2! This is a great way to learn where the elements are on the table and their abbreviations!

Join me later this week for a little more chemistry fun!