8/3/11 - the Noble Gases

In today's excerpt - the Noble Gases, also known as inert gases, are located in column eighteen on the far right side of the Periodic Table of Elements and consist of: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). Each of these gases, under standard conditions, is odorless, colorless, monatomic gases, with very low chemical reactivity:

"Noble is an archaic, funny-sounding word, less chemistry than ethics or philoso­phy. And indeed, the term 'noble gases' goes back to the birth­place of Western philosophy, ancient Greece. There, after his fellow Greeks Leucippus and Democritus invented the idea of atoms, Plato minted the word "elements" (in Greek, stoicheia) as a general term for different small particles of matter. Plato­—who left Athens for his own safety after the death of his mentor, Socrates, around 400 BC and wandered around writing philoso­phy for years—of course lacked knowledge of what an element really is in chemistry terms. But if he had known, he no doubt would have selected the elements on the eastern edge of the table, especially helium, as his favorites.

"In his dialogue on love and the erotic, The Symposium, Plato claimed that every being longs to find its complement, its miss­ing half. When applied to people, this implies passion and sex and all the troubles that accompany passion and sex. In addi­tion, Plato emphasized throughout his dialogues that abstract and unchanging things are intrinsically more noble than things that grub around and interact with gross matter. ...

"Helium is also the best example of 'element-ness'—a substance that cannot be broken down or altered by normal, chemical means. It took scientists 2,200 years, from Greece in 400 BC to Europe in 1800 AD, to grasp what elements really are, because most are too changeable. It was hard to see what made carbon carbon when it appeared in thousands of compounds, all with different properties. Today we would say that carbon dioxide, for instance, isn't an element because one molecule of it divides into carbon and oxygen. But carbon and oxygen are elements because you cannot divide them more finely without destroying them. Returning to the theme of The Symposium and Plato's theory of erotic longing for a missing half, we find that virtually every element seeks out other atoms to form bonds with, bonds that mask its nature. Even most "pure" elements, such as oxygen molecules in the air (O2), always appear as com­posites in nature. Yet scientists might have figured out what elements are much sooner had they known about helium, which has never reacted with another substance, has never been any­thing but a pure element.

"Helium acts this way for a reason. All atoms contain nega­tive particles called electrons, which reside in different tiers, or energy levels, inside the atom. The levels are nested concentrically inside each other, and each level needs a certain num­ber of electrons to fill itself and feel satisfied. In the innermost level, that number is two. In other levels, it's usually eight. Ele­ments normally have equal numbers of negative electrons and positive particles called protons, so they're electrically neutral. Electrons, however, can be freely traded between atoms, and when atoms lose or gain electrons, they form charged atoms called ions.

"What's important to know is that atoms fill their inner, lower-energy levels as full as possible with their own elec­trons, then either shed, share, or steal electrons to secure the right number in the outermost level. Some elements share or trade electrons diplomatically, while others act very, very nasty. That's half of chemistry in one sentence: atoms that don't have enough electrons in the outer level will fight, barter, beg, make and break alliances, or do whatever they must to get the right number.

"Helium, element two, has exactly the number of electrons it needs to fill its only level. This "closed" configuration gives helium tremendous independence, because it doesn't need to interact with other atoms or share or steal electrons to feel satis­fied. Helium has found its erotic complement in itself. What's more, that same configuration extends down the entire eigh­teenth column beneath helium—the gases neon, argon, krypton, xenon, and radon. All these elements have closed shells with full complements of electrons, so none of them reacts with anything under normal conditions. That's why, despite all the fervid activ­ity to identify and label elements in the 1800s—including the development of the periodic table itself—no one isolated a sin­gle gas from column eighteen before 1895. That aloofness from everyday experience, so like his ideal spheres and triangles, would have charmed Plato. And it was that sense the scientists who dis­covered helium and its brethren on earth were trying to evoke with the name 'noble gases.' Or to put it in Plato-like words, "He who adores the perfect and unchangeable and scorns the corruptible and ignoble will prefer the noble gases, by far, to all other elements. For they never vary, never waver, never pander to other elements like hoi polloi offering cheap wares in the marketplace. They are incorruptible and ideal."

"The repose of the noble gases is rare, however. One col­umn to the west sits the most energetic and reactive gases on the periodic table, the halogens. And if you think of the table wrapping around like a Mercator map, so that east meets west and column eighteen meets column one, even more violent ele­ments appear on the western edge, the alkali metals. The paci­fist noble gases are a demilitarized zone surrounded by unstable neighbors."


Sam Kean


The Disappearing Spoon: And Other True Tales of Madness, Love and the History of the World from the Periodic Table of the Elements


Back Bay Book, Little Brown and Company


Copyright 2011 by Sam Kean


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