More notes on "The Disappearing Spoon"

[continued from previous post]

Part I   "Orientation: Column By Column, Row by Row"

1. Geography Is Destiny: H, He, B, Be, Sb
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Page 21, bottom of page:

Egyptian women were applying a different form of antimony as mascara, both to decorate their faces and to give themselves witchlike powers to cast the evil eye on enemies.

They used stibnite in which you can still see the Latin origin of antimony's chemical symbol, Sb. Stibnite gave the blueish black look which is still alluring, though antimony has been removed from reformulated modern eyeliner. The alchemist's symbol for antimony is:

which sort of resembles an upside down version of the female symbol.
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Kean writes at length about Gilbert N. Lewis, as have I. My take on him is here and here.
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Now on to some substantive descriptive chemistry: Page 24, bottom:

As we move horizontally across the periodic table, each element has one more electron than it neighbor to the left. Sodium, element eleven, normally has eleven electrons; magnesium, element 12, has twelve electrons; and so on. As elements swell in size, they not only sort electrons into energy levels, they also store those electrons in different shaped bunks, called shells.

Early German quantum mechanics called this Aufbau or building up. Kean describes how electrons build shells -- s, p, d, and f orbitals -- in a logical way. His descriptions of p-orbitals as a "misshapen lung" and "d-orbitals" as balloon animals is amusing, but I would explain it differently. They more resemble blobs with 0, 1, 2, and 3 nodes as described here.

What Aufbau builds on is how electrons self-organize around an increasingly charged nucleus in moving from hydrogen to higher and higher elements. Start with the simplest atom having one proton and one electron. The very first electron goes into a spherical shaped 1s orbital surrounding the proton. Now if we add another proton to that picture to get to the next element (helium), we must add a second electron. It too goes into the same 1s-orbital and two electrons are happy as clams--perfectly-paired. The pairing of electrons is one of the most sublime aspects of electronic theory and is one which I struggle to understand.

Now move on to element 3, lithium: the third electron cannot occupy the same orbital space as its first two, so it must go into a higher energy orbital, the so-call 2s orbital. The 2s orbital is not exactly just a larger s-orbital; it actually interleaves with the 1s orbital as I drew attention to here:

The fourth electron in element 4, beryllium, perfectly pairs with the third one and fills the 2s orbital. Now, the fifth electron in boron could go into what's called a 3s orbital depicted above, i.e., electrons could just keep building higher and higher energy shells of spherical symmetry, but something else happens. A different type of node appears which breaks the spherical symmetry, creating what's called a p-orbital:

The 2p-orbitals are lower in energy than the 3s orbitals and that's why the next 6 electrons fill those first. There are 6 spaces because the electrons pair and go into 3 different p-orbitals -- one for each Cartesian dimension, x, y, and z.

[more soon]

"Rutherford was an artist. All his experiments had style."

Ernest Rutherford (1871-1937)

Ernest Rutherford reminds me of Michael Faraday. Born in humble circumstances in faraway New Zealand, he travelled to the mother country to study physics. Like Faraday, equal opportunity earned him a place with the best of his day and this meant the Cavendish Laboratory at the University of Cambridge. Rutherford must have witnessed J.J. Thomson's discovery of the electron there in 1897 but there's no record of him taking part in that work. It didn't matter--he had enough in him for two careers in science and a Nobel Prize of his own. And one of Rutherford's great achievements was the accidental undoing of his mentor's plum-pudding model of the atom.

Rutherford's first independent work was the unravelling of radioactivity along with Fredrick Soddy.  More on this later. But first, I want to close a loop I opened a few posts ago by hinting that I had found an inconsistency. I was referring to Richard Rhodes' account of Rutherford receiving the 1908 Nobel Prize in Chemistry:

An eyewitness to the ceremonies said Rutherford looked ridiculously young--he was thirty-seven--and made the speech of the evening. He announced his recent confirmation, only briefly reported the month before, that the alpha particle was in fact helium. The confirming experiment was typically elegant. Rutherford had a glassblower make him a tube with extremely thin walls. He evacuated the glass tube and filled it with radon gas, a fertile source  of alpha particles. The tube was gas tight, but its thin walls allowed alpha particles to escape. Rutherford surrounded the radon tube with another gas tube, pumped out the air between the two tubes and sealed off the space. 'After some days,' he told his Stockholm audience triumphantly, 'a bright spectrum of helium was observed in the outer vessel.' Rutherford's experiments still stun with their simplicity. 'In this Rutherford was an artist,' says a former student. 'All his experiments had style.' 

~Richard Rhodes in "The Making Of The Atomic Bomb"

Rhodes' book is a favorite of mine and I've read it a couple times. But Rhodes makes no mention of Soddy and Ramsey's proof five years earlier that the alpha particle was helium. According to Wikipedia:

In 1903, with Sir William Ramsay at University College London, Soddy verified that the decay of radium produced alpha particles composed of positively charged nuclei of helium. In the experiment a sample of radium was enclosed in a thin walled glass envelope sited within an evacuated glass bulb. Alpha particles could pass through the thin glass wall but were contained within the surrounding glass envelope. After leaving the experiment running for a long period of time a spectral analysis of the contents of the former evacuated space revealed the presence of helium. This element had recently been discovered in the solar spectrum by Bunsen and Kirchoff.* link

This account essentially parallels the elegant (but later) experiment announced in 1908 by Rutherford and described by Rhodes with the exception of radium instead of radon as the source of alpha particles. However, my review of the 1903 Ramsey & Soddy paper cited by the Wiki actually describes a much different and less elegant experiment. link
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*Also, Bunsen and Kirchoff didn't find helium in the solar spectrum--Lockyer did: link

Krypton was hiding in plain sight

original

Perfection can be boring, and so it is with the chemistries of the noble gases. Once argon was discovered 1894, the others were diligently sought and found hiding in liquid air in 1898. First came krypton--its name meaning hidden one--the other two, neon and xenon, were found a few weeks latter. Lord Rayleigh and William Ramsay won the 1904 Nobel Prizes in Physics and Chemistry for their discoveries.
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Helium, the first noble gas, was first found in the solar spectrum, not in thin air.

Neither a Borrower Nor a Lender of Electrons Be

Neither a borrower nor a lender be;
For loan oft loses both itself and friend,
And borrowing dulls the edge of husbandry.
This above all: to thine own self be true,
And it must follow, as the night the day,
Thou canst not then be false to any man.

~Act I, Scene 3 of William Shakespeare's Hamlet

Polonius was speaking of money or gold, giving advice to his own son Laertes. But what sort of miserable person never borrows nor lends money?  A King? Nobility?

The noble gas helium neither borrows nor lends electrons. The price it pays is lonely chemical stability. Helium is the most noble of the noble gases, grudgingly condensing to liquid only at extremely low temperatures.

Hydrogen is the the most common element in the universe and it freely gives, takes, and shares electrons with others. It is the most promiscuous element, forming compounds with practically all other elements except the noble gases.

Those very first two elements display the full range of chemical reactivity and stability--another reason why they sit atop the Periodic Table at opposite ends, bracketing the whole thing as it were. And it's all done with the simplest spherical orbital -- the lowly 1s orbital. Every other heavier element has those same electrons at their very core too. But they aren't part of chemistry -- they're just there -- an inert core. And they're not mere abstractions either--they're part of me as well.

He Watches Over Us

First a few words about spectroscopy. That link has a cool animation of what looks like Pink Floyd’s Dark Side Of The Moon album cover where a prism splits a beam of white light into the colors of the rainbow--the spectrum (pl = spectra) of white light.
Early chemists used colored lines in spectra for the identification of materials when placed in flames.* The flame spectra of individual elements lack the full spectrum of the sun, and more or less resemble a bar code, that is, the spectra have one or several discrete lines separated by spaces. The discrete lines are a “fingerprint” or spectroscopic signature, unique for each element. With that brief introduction, we go back in time to 1868:

On 18 August 1868, a total eclipse of the sun was visible in India, and a number of scientists went there to make observations of the solar prominences. One who examined photographs of the spectra was Joseph Norman Lockyer (1836-1920) who although a civil servant at the War Office had already in his spare time done valuable work in astronomical spectroscopy.
Lockyer was particularly interested in a so called D3 line in the yellow region of solar spectra that had been obtained during the eclipse in India. It was known that the well-known sodium D line was in fact two lines close together, called the D1 and D2 lines. The D3 line could not be obtained from any substance in the laboratory, and Lockyer boldly suggested that it was caused by a new element, found in the sun but apparently not on earth. He gave this new element the name helium, from the Greek helios, the sun.
~The World Of Physical Chemistry, Keith J. Laidler

Lockyer’s hypothesis illustrates one of two ways to advance a theory in science: The first is to amass so much data that the subsequent explanation almost sounds obvious; the second is to boldly assert something with little or no support, and await experimental confirmation.

Helium is the second most abundant element in the universe after hydrogen. Where it does occur naturally on earth, it originates from the radioactive decay of heavier elements. The bulk of our domestic helium supply comes from deposits underground found with gas and oil. Helium is a non-renewable resource: even if made synthetically using radio-decay processes, the supply could not meet demand: link. We recognize helium's use in filling balloons but it is also used in welding and to replace nitrogen in synthetic breathing gas for deep-water diving because its lower solubility in blood minimizes occurrence of the often fatal "bends." However, its greatest use is in liquefied form to cool instruments and for cryogenic research. I used to use lots of it to cool the NMR supercon magnets found associated with nearly every modern chemistry lab.

Helium sits atop the northeast corner of the Periodic Table. From that vantage point, it is possible to look downwards through the eastern border of the chart all the way to the bottom. The elements directly beneath He are the so-called noble or inert elements on account of their general failure to interact chemically with other elements. The other related elements were all given Greek names: Neon (new), Argon (inert) Krypton (hidden), Xenon (strange), and Radon (named after radium but with its suffix changed to conform to the others). The discovery of the noble elements at first confounded the construction of the table--was there another family further to the right? But it was eventually recognized that the noble gas family perfected an understanding of the physical nature of the elements (more on that when we get to Lithium next).

So how many helium balloons would it take to lift a man? Mythbusters apparently did this experiment (I didn’t see it) with helium weather balloons and used about 45 of them, and their balloons were 2.5 meters diameter. I once tried to fill one of those inflatable love dolls (a gag gift) with helium to get it to float for a Halloween party- it didn't work. :(
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*Robert Bunsen was a 19th century German chemist interested in the flame emission spectra of the elements--guess what he invented?