Science by a Scientist: On Molecules
I recently wrote about atoms, the fundamental unit of matter. You can find that here. The article may have caused you to wonder how fewer than 100 types of naturally occurring atoms form the basis of all we see. The answer is molecules.
Baking
Let’s base the explanation on an illustration: The Great British Bake Off. We love to watch this, seeing how a dozen or so hapless contestants compete by baking breads, cookies, pastry, and cake—so many variations! And yet, they pretty much all contain flour, sugar, butter, eggs, and a few other ingredients. It’s all in how the ingredients are combined.
Organized Interactions
Atoms also combine. They don’t do it at a contestant’s whim, nor do they obey Paul Hollywood. Instead, they combine based on how many electrons they have in their outer shell. It’s all highly organized.
Remember that atoms are what they are because of their number of protons (+ charge)? And that they have the same number of electrons (– charge) as protons? Well, the electrons don’t hang out where they want. They have specific places, shells. Not only that, they hang out in pairs. Two electrons go into the inner shell. Eight go in the next. And eighteen in the one after that. I won’t bore you with the rest. The electrons fill these shells from the inside to the outside. So, hydrogen (H), which has one proton, has one electron in its shell. Lithium has three protons and has two electrons in its inner shell and one in the next. Beryllium has 2+2. And so it goes.
They Love Being Full
Atoms are most comfortable if their shells are full. If they’re full, the atoms won’t interact at all with anyone and are called noble gases. Maybe think of wealthy royals who don’t need anyone. Helium with two electrons, Neon (Ne) with 2+8, and Argon with 2+8+8 are all noble (but not royal) gases.
Where There’s a Will, There’s a Way
When the outer shell isn’t full, the atom does what it can to make it full. It’ll lose, gain, or share with another atom depending on what is easier. Does that make them lazy? You decide. Anyway, for example, lithium usually gives its extra electron away, and beryllium gives away two. Those entities are now called ions, since they have a charge: +1 or +2. Chlorine has 2+7 electrons. It’s easier for chlorine to gain an electron than lose one, so it does that and becomes an ion with a charge of -1. If the positively charged lithium cation gets near the negatively charged chlorine (chloride), they will stick together, making what chemists call a salt. A commonly known salt is sodium chloride, made when sodium (Na) loses its extra electron, chlorine gains one, and the ions hang out together.
Sharing is Caring
Those who enjoy math may have already figured out that some atoms have 3, 4, or 5 electrons in their outer shell. They could, of course, lose or gain what is needed to be full, but it’s more likely that they will share. So, carbon with 6 protons and 2+4 electrons will share electrons with other atoms. For example, carbon shares its four electrons with four hydrogens, each of which needs one more, making methane. That bond is called covalent. It also shares two electrons with each of two oxygen atoms, creating carbon dioxide. Carbon is very versatile, so it is and must be the basis of life.
Sharing–Kind of
The last molecule that I want to mention is water. It’s made of an oxygen atom sharing electrons with two hydrogen atoms. If you look at the illustration, you’ll quickly notice that oxygen is a bigger atom than hydrogen: it has more protons. The positively-charged protons pull hard on the shared electrons, making the water molecule polar. The electrons spend more time near the oxygen than the hydrogen, so there is a slight positive charge near the hydrogens and a slight negative charge near the oxygen. And THAT causes fleeting interactions called hydrogen bonds that are what make life possible! Seriously!
Life
Well, that’s not all that is needed. Life also uses macromolecules. It is all incredibly organized and complex. And that’s all I’m saying until next time!
