Moment of Science: The Atom

They say you can never trust an atom because they make up everything. This week, we’re shrinking down and getting literally into the heart of the matter.

We’ve covered the periodic table and all its arrangements already, so we’re focusing just on the elements as a whole. The atom is somewhat the most basic unit of all matter -- and the ancient Greeks thought they were the absolute smallest things there were (”atomos” = “uncuttable”/”indivisible”) -- but atoms also have smaller subatomic particles: positively-charged protons and neutral neutrons to make up that nucleus in the center, and negatively-charged electrons that orbit around. Much like the far reaches of the universe, atoms are more than 99% empty space -- sort of. Our idea of empty space breaks down at the atomic level, and electron clouds technically fill in the lion’s share. That might clue you in that nearly every visualization of an atom you can picture is probably wrong, though good luck finding a better one to fit on your screen.

The nucleus is so concentrated that it’s only about one hundred-thousandth of an atom’s width -- and the strong force holding those protons and neutrons together is more than 100 trillion trillion trillion times stronger than gravity. (That’s a direct quote from NASA, by the way.) Atoms of different elements have a different number of protons. Carbon atoms have 6 protons and 6 neutrons in their nuclei, helium goes 2 for 2, though hydrogen has just the one proton and no neutrons. That makes it the smallest atom at a mere 106 picometers wide, yet hydrogen makes for nearly 3/4 of all atoms in our galaxy. On the other end, cesium -- one of the largest, is nearly 6 times wider... though it also has a bunch more electrons to work with.

Speaking of those electrons, they’re so small that more than 1800 of them could fit in just one proton. They spin so fast that it’s hard to know exactly where they are, so we just kind of fudge it into “orbitals” where they’re most likely to be found. Atoms are electrically neutral, so gaining electrons makes the atom more negatively-charged, and losing them makes a positive atom. Voila: that’s how you get “ions”.

Some atoms are so unstable that they simply decay and get rid of particles, giving off energy with no outside help. That’s a radioactive situation, and splitting those nuclei manually is how you achieve “fission”, in either bombs or power plants.

But wait, there’s more! Protons and neutrons are themselves made of even tinier bits. Quarks are the smallest things we know of -- and there’s three in every proton and neutron, with “gluons” staying true to their name and gluing them all together to look like a subatomic fidget spinner.

We’ll get into molecules and states of matter all that at a later date, but consider this for a final note: If you can’t picture how small an atom is, your body is made of about 7 octillion of them... maybe slightly less if you’ve been hitting the gym lately.

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