Elementary History

<chirp, chirp> “Moire here.”

“Hi, Sy, it’s Susan.”

“Well, hello. Good to hear from you. What’s up?”

“I’m out here on my back porch, fooling around on my laptop. It’s too nice to work in the lab today.”

“I agree with you. I’m outside, too, enjoying the Springtime. What’s your fooling around?”

“I found a discovery date list for all the chemical elements. Guess which element was the first that humanity worked with in pure form?”

“Mmm, I’d say carbon, in charcoal.”

“Nope, it’s copper.”

“Copper?”

“Mm-hm. Or maybe gold. They both occur as the raw metal but copper’s more common. There was a Copper Age before the Bronze age. The dates are fuzzy because they depend on what the archaeologists find after site scavengers have been there. I’m sending you the first few rows from the list.

Cumulative
Count
Element
(Symbol)
Atomic
number
Estimated
years ago
1Copper (Cu)2910000
2Lead (Pb)826000
3Carbon (C)65750
4Silver (Ag)475000
5Tin (Sn)505000
6Antimony (Sb)515000
7Gold (Au)794500
8Iron (Fe)264000
9Mercury (Hg)803500
10Sulfur (S)162500

“You can win most of them from the right ore with relatively simple processing. It makes sense they’re the ones we got to first.”

“Susan, I’m surprised it took a thousand years to realize you can get sulfur from cinnabar ore at the same time you’re cooking the mercury out of it. I wouldn’t want to be downwind from that process or most of the rest.”

“Sure not. I’ll bet there just wasn’t much interest in sulfur until the alchemists started playing with it. Anyhow, I dumped the element data into a spreadsheet and got some fun facts when I graphed it. Look at this. Eight thousand years for 10 elements through sulfur, then 1800 years of nothing. Arsenic doesn’t show up until the Thirteenth Century when I guess royalty started using it to poison each other. And phosphorus — have you read Neal Stephenson’s Baroque Cycle trilogy?”

“Yes, and I know the episode you’re thinking of, where the hero routed a gang at night by coating himself with glowing phosphorus and bursting out of a cave pretending to be a demon. Stephenson put a lot of words into describing how factories obtained mercury and phosphorus back then.”

“Stephenson puts a lot of words into most everything nerdy. That’s why I enjoy reading him. Oh-ho, now I know how you knew about cinnabar being the source for mercury.”

“Hey, Susan, I don’t only do Physics, but yeah, that was from another Baroque Cycle episode. … Looking at your graph here — things certainly took off at the start of the Eighteenth Century.”

“Yes, indeed. Seventy-four elements, everything that’s not radioactive plus a couple that are. I get a chuckle from cobalt being the first element in that wave after phosphorus. You know the story?”

“What story is that?”

“Seventeenth Century miners kept digging up nasty rocks that emitted poisonous gas when smelted along with the desirable copper and nickel ores. They called the bad stuff kobald Oren, German for ‘goblin ores.’ When a Swedish chemist finally purified the material he simply re-spelled the adjective and called the metal cobalt. I love the linkage with Stephenson’s fictional phosphorus-covered demon.”

“Cute. Why the break between rhenium and technitium?”

“That second wave after 1935 is all radioactives. Funny how the timing paralleled Seaborg’s research career even though he never got involved with technitium, the first artificially-produced element. Imagine being the discoverer of ten different elements.”

“Seaborg practically invented that funny bottom row of the Periodic Table, didn’t he?”

“Oh, yes. Not only did he discover or co-discover more than half of those elements, he was the one who proposed setting off the entire group as Actinides, in parallel with the Lanthanides above them. Oh, that reminds me, I meant to show you the other display I built. You’ve probably never seen one like this.”

“Whoa, you’ve colored each element block by how long we’ve known about it. That’s not the kind of thing you can do with crayons.”

“No, I had to do some programming to get the right tints.”

“What’s the little star for in the middle of the scale?”

“That’s when Mendeleev first proposed the Table, smack in the logarithmic center of my timeline. Don’t you love it?”

~~ Rich Olcott

Three atop A Crosshatch

“Hey, Sy, what you said back there, ‘three and a fraction‘ ways to link atoms together…”

“Yeah, Vinnie?”

“What’s that about?  How do fractions come in when you’re counting?”

“Well, I was thinking about how atoms in separate molecules can interact short of reacting and forming new molecular orbitals.  I figure that as a fraction.”

Charge sharing ain’t the whole story?”

“It would be except that sharing usually isn’t equal.  It depends on where the atoms are in the Periodic Table.”

“What’s it got to do with the Periodic Table?”

“The Table’s structure reflects atom structures — how many shells are active in a base-state atom of each element and how many units of charge are in its outermost shell.  Hydrogen and Helium are in Row 1 because the 1-node shell is the only active one in those atoms.  The atoms from Lithium to Neon in Row 2 have charge activating both the 1-node shell and the 2-node shell, and so on.”

“What’s that get us?”

“It gets us a feel for how the atoms behave.  You know I’m all about dimensions, right?”

“Ohhh, yeah.”

“OK, we’ve got a two-dimensional table here.  Going across, each atom’s nucleus has one more proton than its buddy to the left.  What’s that going to do to the electronic charge?”

“Gonna pull it in closer.”

“Wait, Vinnie, there’s an extra electron in there, too.  Won’t that cancel out the proton, Sy?”

“Good thinking, Eddie.  Yes, it does, but only partially.  The atoms do get smaller as you go across, but it’s irregular because negative-negative repulsion within a shell works to expand it almost as much as negative-positive attraction contracts it.”

“Bet things get bigger as you go down the Table, though.”

“Mostly, Vinnie, because each row down adds a shell that’s bigger than the shrinking inner shells.”

“Mostly?”

“The bigger shells with more nodes have more complex charge patterns than just balls and dumbbells.  Those two rows below the main table actually squinch into the lowest two boxes in the third column.  In those elements, some of the activated patterns barely shield the nucleus.  The atoms to their right in the main table are almost identical in size to the elements above them.”

“So I can guess an atom’s size.  So what?”

“So that and the charge give you a handle on the element’s properties and chemistry.  Up there in the top right corner you’ve got the atoms with the highest ratio of nuclear charge to size.  If given the opportunity to pull charge from atoms to their left and below them, what do you suppose happens?”

“You get lop-sided bonds, I guess.”

“Exactly.  In water, for instance, the Oxygen pulls charge towards itself and away from the Hydrogen atoms.  That makes each O-H bond a little dipole, positive-ish at the hydrogen end and negative-ish at the oxygen end.”

“Won’t the positive-ish ends pull on the negative-ish parts of next-door molecules?”

“You’ve just invented hydrogen bonding, Eddie.  That’s exactly what happens in liquid water.  Each molecule can link up like that with many adjacent ones and build a huge but floppy structure.  It’s floppy because hydrogen bonds are nowhere near as strong as orbital-sharing bonds.  Even so, the energy required to move through liquid H2O or to vaporize it is much greater than for liquid methane (CH4), ammonia (NH3) or any similar molecule.”

“Can that pull-away action go all the way?”

“You’ve just invented ionic bonding, Vinnie.  The elements in the Oxygen and Fluorine columns can extract charge completely away from many of those far to the left and below them.  Fluorine steals charge from Lithium, for instance.  Fluoride ions are net negative, lithium ions are net positive.  Opposites attract, same as always, but now it’s  entire ions that attract each other and you get crystals.”

“That’s your and-a-fraction?”

“Not quite, Vinnie.  There’s one more, Van der Waals forces.  They come from momentary polarizations as electron chaos sloshes back and forth in neighboring molecules.  They’re why solids are solid even without ionic or hydrogen bonding.”

“Geez, look at the time.  Rosalie’s got my dinner waiting.  Bye, guys, everybody out!”

~~ Rich Olcott