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30-Second Elements ed by Eric Scerri30-Second Elements: The 50 Most Significant Elements, Each Explained in Half a Minute, ed. Eric Scerri (Icon 2013)

Pythagoras thought the world was governed by whole numbers and their ratios. He was wrong, but you could still call chemistry a Pythagorean subject. The huge difference between, say, the noble gas neon and the alkali metal sodium is actually based on a tiny difference in protons. Neon has ten, sodium has eleven. That’s why the two of them behave so differently. As Hugh Aldersey-Williams says on page 64: “Neon is so inert that it forms no chemical compounds at all.” But Brian Clegg says this of sodium on page 16:

This soft, silver-tinted alkali metal is known for its reactivity. Drop a small piece into water and it will fizz energetically as it converts to sodium hydroxide and hydrogen, giving off plenty of heat.

The atomic weight of an element, or the number of positively charged protons it has, affects the number of negatively charged electrons it has. Electrons and their arrangement determine how an element reacts with itself and with other elements. So one proton extra can make a huge difference: it can tip the balance between one configuration of electrons and another, between the inertness of neon and extreme reactivity of sodium.

And sodium obviously isn’t something you’d want to put in your mouth. Except that it is. Sodium is essential for life and isn’t dangerous when ingested as part of the compound NaCl, a.k.a. sodium chloride, a.k.a. table salt. The other half of the compound, chlorine, is also dangerous in its free state: when breathed in, it “burns away the lining of the lungs, leaving victims drowning the fluid that oozes out” (pg. 54).

Elsewhere, carbon and oxygen are the opposite: benign or essential for life when they exist as free elements, but potentially deadly in combination as CO, carbon monoxide, or CO2, carbon dioxide. Chemistry is a complicated business, but there is an underlying simplicity in the whole numbers that represent sub-atomic particles: protons, electrons and neutrons.

This simplicity is laid out in the periodic table, which was proposed and perfected by the Russian chemist Dmitri Mendeleev (1834-1907) in the nineteenth century. As explained in the introduction to this book, the table arranges elements in columns and elements in the same column share chemical properties. Neon is in the column of noble gases, on the far right, while sodium is in the column of alkali metals, on the far left. An extra proton turns helium into lithium, neon into sodium, argon into potassium, krypton into rubidium, and so on. A small change in atomic weight translates into a huge change in chemical behaviour.

An extra proton also turns platinum into gold and gold into mercury. But the transitions in behaviour aren’t as sharp in the inner columns of the periodic table: all of those elements are metals, even though mercury is liquid at room temperature. It’s also poisonous and when it was used to “treat animal fur in hat-making”, it inspired “the phrase ‘mad as a hatter’ and the character of the Hatter in Lewis Carroll’s 1865 novel Alice’s Adventures in Wonderland” (pg. 90). The double-page elemental biographies discuss culture as well as chemistry and chemists, but they’re all brief and this is a primer, not a proper scientific text.

And one page of each biography is occupied by an image: 30-Second Elements is a book for the internet age and its short attention spans. But the images are colourful and inventive – a glowing skeleton dancing amid seashells for “Calcium”; diamonds surrounding a cut-away earth for “Carbon”; the Statue of Liberty atop coils of tubing for “Copper” – and they capture the spirit of chemistry, both as a subject and as a phenomenon. Chemistry is rich, exuberant and endlessly fascinating. All its big names and big discoverers are here, from Lavoisier, Mendeleev and Humphrey Davy to William Ramsey, Marie Curie and Glenn Seaborg.

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