The Joy of Chemistry

How many different substances do you think there are in the universe? Millions? Billions?

The truth is, largely because of the versatility of the carbon atom, the number is potentially infinite.

But how many different particles do you think it takes to describe the composition of that infinity of substances?

The answer, which was unravelled by chemists a century or more ago, and is the triumph of chemistry, is just two.

I’ll say it again. Just two. That fact which I learned at the age of 14 just blew my mind, and changed the course of my life. Follow on down, and I’ll make a chemist of you too!

During the previous years my interests had revolved around the natural sciences. I had all the relevant Observer’s pocket books: birds, flowers, trees, fish, insects, although my prime interest was birds and I had the three volumes of Coward’s Birds of the British Isles and their Eggs. The first two years of General Science in Grammar School passed without note but in Form 3 (I think that is year 10 today?) we had a biology teacher. I was always asking him questions and quoting from my books. I think he thought I was trying to upstage him, but it was just intense interest which he interpreted as impertinent challenges to his authority. I progressively lost interest and going into the Fourth while I took the sciences I opted for German instead of biology, a future potential career as a medic was buried, and I was destined to become a chemist, and later an electrochemist. Electrochemistry is where chemistry meets electricity, and if that sounds abstruse, well you are all familiar with batteries.

Our chemistry teacher was a short fat man and he kept the class rapt with his wit and oration. A school friend and I kept a notebook to record his sayings, which ensured that we paid close attention. On one occasion, referring to his corpulence, he told us: ”I have stopped playing golf, because when I put the ball where I can see it, I can’t reach it; and when I put it where I can reach it, I can’t see it”. I got seriously absorbed in chemistry to the extent that it was the only subject in which I kept abreast of lessons by reading ahead in the text book: so I learned everything, in effect, twice. And then we came to that revelation. I was thunderstruck. How powerful was that science! That’s my kind of subject! Chemists must be masters of the universe!

I studied Chemical Engineering at Swansea University for one year. I didn’t enjoy it, did no work, failed the end of year exam and got booted out. My girl friend’s brother-in-law at that time was the training officer for BP and he put me on a four year sandwich course in London (nepotism, what?), each year six months in college and six at the BP Research Centre at Sunbury on Thames. One afternoon in October 1965 when I was working in the Gas Analysis lab, just as I was shutting the equipment down, a bunch of suits came in, and one handed me a gas sample. I ran it on the Beckman C1 to C4. After a few minutes the result came out and I told them it was 99% methane. A great cheer went up and they filed out. A few days later I was told that I had analysed the first sample from the North Sea gas field which was to power the UK for decades.

Subsequently most of my professional life has centred on chemistry. When I couldn’t get a research job I went into teaching. My first such job was as second in command of a chemistry department in a secondary comprehensive school in the South Wales valleys. My boss kept all the academic work and I spent most of the time teaching general science with the non-academics, they would mostly sit no exams at all: when the leaving age went up from 15 to 16 most of them voted with their feet in that final year, and I would be left with a class of four or five. I just ignored the curriculum which was a totally unsatisfactory watering down of the academic syllabuses. I tried to find things that would interest them so I taught them first aid, and we went out on country walks to learn the names of the birds, the flowers, the trees. Nobody cared. Later on I was the sole chemistry lecturing inhabitant of a college of further education, I had a teaching lab all to myself, and this enabled me in my spare time to get research done which eventually led to a successful business and permanent liberation from teaching.

In between those interludes I worked on breathalyser development, and in 1983 I directed the world’s first countrywide mass introduction, into police stations in Britain, of evidential breath alcohol equipment, that which produces a result on a piece of paper for the law court, 628 units in all.

But I digress.

Before I take you further into the chemists’ secret world of sub-atomic particles I need to point out that things started to unravel in 1932 when it was found that a third particle was needed to complete the job. Then in subsequent years, it was shown that those particles in fact themselves consisted of various combinations of yet smaller particles. But nevertheless, for we chemists the original two particle theory is sufficient to do most of the necessary.

We can move first from the infinite to 92, because that is the traditional total of basic building blocks - the elements - that make up all substances. Another striking example of the beauty that is chemistry was the story of how 19th century chemists… I interrupt myself here to observe that those people who sell pills in high street shops are not chemists, they are pharmacists…  those 19th century chemists noticed on the way to building up that picture of 92 root substances that many of them seemed to form kinds of families because they behaved in similar ways, and when they were organised on paper there seemed to be gaps in the pattern. They supposed that in these gaps were elements as yet undiscovered, and they predicted the ways in which they would behave if found and investigated. And they were right!

The full pattern is now laid out in the Periodic Table of the Elements, listed as their symbol abbreviations. Interestingly, they are nearly all metals, the few non-metals being Hydrogen and the more brightly coloured on the far right, plus those on the border - Boron, Silicon, Arsenic, Tellurium and Astatine. Most of the abbreviations are obviously derived from their common names, but some seem to have no connection. I think these mostly derive from the Latin: sodium Na, potassium K, iron Fe; antimony Sb made me curious, it’s from its main mineral, stibnite.

Let’s now proceed to build up that table of the elements. Atoms are pictured as miniature solar systems, with positively charged protons, tiny particles as the sun at the centre, and even much smaller particles, the negatively charged electrons, as the planets, kept in place by their opposite charge to the protons. Electrons are what travel along wires to give you electricity. When atoms pack together to create solids, they cannot get closer than the outermost orbiting electrons. This results in the second most extraordinary fact about matter, which is that it is almost 100% empty space (1). I’ll just mention here that the third particles, the neutrons, also sit in the nucleus and help to bind the protons together, and then forget them.

The first, simplest atom is hydrogen (H) with just one proton in the nucleus and one electron in the orbit (or shell). Number two is helium (He) with two of each. At this stage the first orbit is considered to be full and the second orbit begins outside the first. Number three is lithium (Li) with three protons in the nucleus, two electrons in the first orbit and just one electron in its new orbit. That holds eight electrons, when full that is element number ten, Neon (Ne). Then the next orbit starts with number eleven, sodium (Na), with one outermost electron, like lithium, and as I said above, the consequence is that lithium and sodium are chemically similar. This orbit also holds eight, and that goes up to Argon (Ar).

The next orbit starts with potassium, and as you will guess, it is chemically similar to lithium and sodium, being in the vertical “family” group 1 in the Table. If we carried on to the end in like manner we would encounter rubidium (Rb), caesium (Cs) and francium (Fr) all in Group 1, and as you have guessed, they are chemically very similar to lithium, sodium and potassium. They are all highly reactive, attacking water. Lithium being the lightest element is the best choice for batteries because it carries the least dead weight per reactive electron. The weight ratio of lead, the original battery constituent, to lithium, the modern favourite, is 30:1, but lead offers two electrons to lithium’s one, so the effective ratio is 15:1!

Here below is element 18: can you identify it?

Yes, it is Argon. Did you notice that atoms like this with full orbits constitute the inert (unreactive) gases helium, neon, and argon? That is because for one atom to combine (react) with another to produce a new substance, it needs to have part filled orbits whose electrons are said to be reactive, that is to say that they can interact with other such reactive atoms. Such reactions involve either the transfer of electrons from one set of atoms to another to make (for example) common salt, sodium chloride NaCl, or sharing to make (for example) water, H₂O. But that is something we may consider at a later date, if interest persists.

I said at the outset that there were originally 92 elements but in the table you will have seen that they now go up to 118. These additional ones were not hiding down the back of the sofa, but have been progressively synthesised, most last just seconds or fractions of a second before breaking down into smaller atoms, plutonium (94) an exception, which of course has been accumulated in weapon systems. Here is a table of half-lives of the super heavy atoms, as you can see they are very short-lived - their decay follows a fixed rule, the half-life, that half breaks down in a fixed time, then the next half the same elapsed time, and so on. I have to say I don’t know much else about them as they have all emerged I think since my first degree education ended.

1. To get some idea of how much space there is in an atom, consider what happens if you join each electron to a proton to turn all the mass into neutrons, and pack them close together taking out all that empty space. This is what happens when a neutron star is formed. The density is colossal: a matchbox sized quantity would weigh about 3 billion tonnes, as much mass as an 800 metre cube of Earth material. A consequence of this loss of volume is that as it collapses, its rotation speed rises to maintain the angular momentum. Some such stars (pulsars) emit a beam of radiation enabling detection, and the fastest known rotates at 43,000 revolution per minute, the surface travelling at a quarter of the speed of light. There may be a billion of them up there. And if the neutron star collapses even further it becomes a black hole, whose gravity is so great that even light cannot escape. Presumably the neutrons have collapsed further, but nobody knows what is inside and it’s not going to be easy to find out.