Gallium Arsenide is Germane to Solar Cells

Gallium arsenide, a simple combination of two elements, interconverts light and electricity; GaAs lasers turn electricity into light and GaAs solar panels convert light back into electricity. There are alternative combinations of elements for these tasks, but each has its limits. What strikes me is how gallium and arsenic bookend germanium:

I need a name for "binary combination of elements which brackets and mimics another element." The term isoelectronic is close but doesn't cut it for me. There is a mathematical symmetry about GaAs in view of Ge and it goes like this: (31 + 33)/2 = 32 or, in chemical logic symbols: (Ga + As)/2 = Ge.

Like gallium arsenide, germanium is a photovoltaic material. Google "germanium solar cell" and you will find cutting edge research involving blends of gallium arsenide with germanium. I'm glad there is on-going research into new materials because I am not sure we should be putting arsenic on every rooftop much like we're putting mercury in every lightbulb.

A similar "bookend relation" occurs a couple rows up in the Table between boron, carbon, and nitrogen. Look how boron and nitrogen bracket carbon:

Once again, (5 + 7)/2 = 6. And just like carbon, boron nitride (BN) has both graphite- and diamond-like structures. One type of BN is even harder than diamonds: link

I see a pattern here: the centrality of the carbon group, C, Si, Ge, etc. to the family of main group elements:

What Is The World's Smelliest Chemical?

Wikipedia corrals some of the suspects here: link  I thought I'd put their mugshots up here. Please vote for your favorite in the comments or suggest your own "worst."

(1) Spermidine, the essence of "funky spunk." 

Spermidine is related to aptly-named cadaverine and putrescine.

(2) Trimethylamine, the essence of "fish taco:"

(3) Butyric Acid, the essence of vomit:

(4) Skatole, an indole & the essence of poop:

(5) Mercaptans--methyl and butyl thiols--the essence of skunk:

R = methyl and butyl

(6) Hydrogen sulfide, H₂S, the essence of rotten eggs and bad farts:

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Runner's up which did not make Wiki's list:
(a) Cacodyl, named from the Greek, meaning "evil-smelling."
(b) Bromine, from Greek βρῶμος, brómos, meaning "stench (of he-goats)"
(c) Cyclohexane thiol: This is technically covered under (5), but to my nose smells like the essence of armpit B.O.

Arsenic's Poisoned Reputation

Arsenic is called the "King of Poisons" and the "Poison of Kings" due to its long history. Interested readers (I'm looking at you, Jason) can GIY or perhaps even suggest a reference in the comments.

Lesser known is arsenic's more recent role in our own poison gas warfare program. I mentioned Lewisite here, but I thought that a more formal introduction was in order. Even a non chemist can recognize arsenic's central role in Lewisite's structure. Here it is:

Lewisite, chemical structure

We made a lot of Lewisite shortly after WW I but we never deployed it as far as I know. Ridding our stockpiles has taken forever and an old cache was recently found in Washington, D.C.  Arsenic just can't doff its nasty reputation, even cloaked in disguise.

Arsenic And Old Lies

Alchemist's symbol for Arsenic

Some credit Arsenic with being present at the miraculous birth of organometallic chemistry. He was not.* Let me explain.

Organometallic chemistry is the mystical, covalent union of metallic elements with non-metallic elements--mainly carbon with metals. Saying that Arsenic is a metal is a bit like saying that Barack Obama is black. Arsenic, like phosphorus and sulfur, has different allotropes which is more a mark of non-metallic character.

The element has been known since at least 1250 A.D, but it was known much earlier as its sulfide and its affinity for sulfur is the chief cause for its toxicity. It binds to vital sulfur-containing proteins in cells and shuts them down.

Only about a dozen or so elements are poisonous (not including radioactive ones); the dirty dozen are (in alphabetical order): Aluminum, Antimony, Arsenic, Barium, Beryllium, Cadmium, Chromium (hexavalent), Lead, Mercury, Osmium, Thallium, and Vanadium.

Each name has its own story and its own LD₅₀--some are much worse than others.
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*He because the word Arsenic derives from a Greek word corresponding to male potency. Link

Meet the Priest who invented Flubber

Remember the storyline from Walt Disney's The Absent Minded Professor(1961)?  Fred MacMurray played a small Midwestern college chemistry professor who invented a miraculous substance which he named Flubber. He saved the football team and got the girl in the end. I think I found the real-life embodiment-well, forget the getting the girl part and focus on the chemistry and small midwestern university parts.

Reverend Julius Nieuwland (1878-1936)

I ran across the name Julius Nieuwland recently. Nieuwland was a priest and professor at Notre Dame University. As part of his Ph.D research, Nieuwland discovered Lewisite which was produced in tonnage quantitites by the U.S. during World War I as a poison gas.  Nieuwland had nothing to do with this application and distanced himself from the molecule (it's named for an enthusiastic supporter of gas warfare, named Lewis). Later, as a professor of organic chemistry at Notre Dame, Nieuwland successfully polymerized acetylene into divinylacetylene, laying the groundwork for the discovery of neoprene by Du Pont.

One of Nieuwland's more famous students was Knute Rockne, which even explains the football part of the otherwise bizarre Flubber story.