Ch 2.2: Periodic Table Time

When you look at the periodic table, You’ll always see at least two numbers for each element listed. The smaller number is known as the atomic number and as easily seen, it goes one, two, three, all the way to one hundred eighteen as you move across and then down the table. More on what the atomic number is in five sentences. The other number (the bigger one) is the atomic mass. It’s usually some number followed by some decimal points (something like 12.01 in the case of carbon) and what that number represents is the weighted average of the atomic masses of the isotopes of that element. Lots of science words but stay with me as we work backwards through that sentence. An element is the most fundamental type of atom. Each element has a distinct number of protons, and that number of neutrons is what the other number on the periodic table tells us. Going back to carbon (because its a dope element and super important, more on that shortly), it has an atomic number of six, which means EVERY SINGLE ATOM of carbon in the fucking UNIVERSE has six protons. Let me say that again but in a different way because its super fucking important -- if any atom in the entire known and unknown universe has six protons, it HAS to be carbon. I screwed these last two sentences up the first time I wrote this because I was doing it at eight in the morning on a Saturday and accidentally wrote twelve (which is carbon’s mass) but carbon can’t have twelve protons because if an atom had twelve protons, it would be magnesium. Back to the good ol’ peanut M&M analogy, every single peanut M&M has to have a peanut at its center because otherwise it wouldn’t be a peanut M&M.

Just like the candy, which can have a bigger or smaller nut (insert joke from two paragraphs ago), carbon can have a bigger or smaller nucleus. How does this happen? By changing the number of neutrons. When you compare two atoms and they have the same number of protons but a different number of neutrons, they are what’s known as isotopes. Carbon has a bunch of different isotopes but some of the more famous ones are carbon-12, carbon-11, and carbon-14. Writing their names like this, with the element’s name followed by a number, we can actually get a lot of information if we’re smart enough to understand what the hell is going on. The word carbon tells us six protons because carbon’s atomic number is six and atomic number = number of protons. The numbers eleven, twelve, and fourteen tell us the atomic mass of that isotope, which is something we actually discussed earlier when the idea of the atomic nucleus was introduced. If you already forgot what you read three paragraphs ago, the nucleus of an atom contains all the protons and neutrons, so the atomic mass is equal to the number of protons (in this case, six) plus the number of neutrons. Carbon-11 has six protons and five neutrons. Carbon-12 still has six protons but this version of carbon has six neutrons, giving a mass of twelve. Lastly for this example, carbon-14 has, you guessed it, six protons and eight neutrons.

Also for each element, you’d have to be super dumb to not notice that every element has an abbreviation. Some are (hopefully) super obvious like C for carbon, H for hydrogen, O for oxygen, etc, but others, like those for potassium and lead, are definitely not obvious. Potassium is K, from the latin word for alkali (kali) which came from an arabic word meaning “plant ashes” People back in the day would burn trees to create potash, which is a substance used both as fertilizer and in the making of cement, and that’s why we abbreviate potassium with a K. The abbreviation for lead, Pb, is from the Latin word plumbum which means, oddly enough, lead.

The last thing related to the periodic table I want to talk about is how the number of valence electrons change as you move sideways across the table. Each column is called a group and starting in group one, with hydrogen, you have one valence electron. Group two has two, then things get fucked up in the middle and that’s another something for Chemistry for Bastards to cover, then group three has three valence electrons etc all the way until you get to group eight. What makes this important is the fact that atoms with the same number of valence electrons will tend to react the same. What do I mean by react? Well…