In my first year at secondary school, which I entered at age 12½, we were given taster classes in science: an hour a week each of chemistry, biology, and physics. I remember that when the physics teacher had explained to us how an electric bell worked I asked him what determined the frequency of the beats in the ringing. But instead of giving me a serious answer, perhaps involving either the dimensions and elasticity of the vibrating clapper or the characteristics of the current applied, he sarcastically replied, “Why don’t you count them?”. This rather put me off physics. The chemistry teacher, on the other hand, showed us sodium, manganese, potassium, and other elements, and did experiments involving explosions and brightly coloured flames. He even demonstrated a Geiger counter and sources of alpha, beta and gamma rays. When I let slip that I knew that the lead (Pb) resulting from the radioactive decay of thorium has a different atomic weight from that of ordinary lead, he was so excited that he made a serious effort to recruit me to study science. But I had just started classical Greek, and I decided to stick with that, while continuing (as I do to this day) to read popular science books in my spare time and try to be reasonably well-informed about scientific subjects.
So you will understand that when I came to make a dictionary I took it as obvious that the headword list should include, for example, the names of all the chemical elements. I noticed with amusement that Daniel Jones’s EPD had ytterbium and yttrium, but not the other two elements named after the ore mines at Ytterby in Sweden, namely erbium and terbium. Naturally, LPD has all four (as does the current Cambridge EPD).
…which brings me to the question of element number 51, Sb, antimony. At school I acquired the pronunciation ænˈtɪməni for this element, with antepenultimate stress. This is also the pronunciation recorded in Daniel Jones’s EPD, at least up to and including the twelfth edition (1963). However, when Gimson took over the editorship for the fourteenth edition (1977), he added (and prioritized) the initial-stressed ˈæntɪməni. The on-line OED gives only this latter; whether this is the pronunciation recorded in 1885 or one reflecting a more recent editorial decision I do not know. After informally consulting colleagues in the chemistry department, I also decided to go with this in LPD. Merriam-Webster shows the same initial stress, but with a strong (‘stressed’) penultimate vowel, ˈæntəˌmoʊni, so bringing it into line with such words as testimony, alimony, ceremony. For what it’s worth, the -mony part of antimony does not seem to derive from the classical Latin -mōnium that we see in these words (nor from the ‘anti-monk’ origin given by Dr Johnson, which the OED calls an ‘idle tale’). The OED thinks it is ‘probably, like other terms of alchemy, a corruption of some Arabic word, refashioned so as to wear a Greek or Latin aspect’.
Nor is this chemical term to be confused with the philosophers’ antinomy (though it sometimes is).
When I was young relatively few transuranic elements had been named. As Tom Lehrer sang in 1959, the 102 elements then known were “the only ones of which the news has come to Ha’vard | and there may be many others, but they haven’t been discavard”. So in LPD I’ve got lawrencium, rutherfordium and dubnium, but not seaborgium, bohrium, hassium, meitnerium, or darmstadtium, still less such exotic newcomers as roentgenium and ununtrium. According to Hugh Aldersley’s recent book Periodic Tales, the International Union of Pure and Applied Chemistry, the organization in charge of ratifying chemical nomenclature, requires each new element to have a name ‘that is easily pronounced’. It’s not clear to me what that means in the last three cases I have mentioned, in each of which there is more than one possibility in English that could be supported by the spelling.