One or two letters

About this video

Chemists write about 118 elements again and again, so each one has a short name of one or two letters: its chemical symbol. The idea comes from the Swedish chemist Jöns Jacob Berzelius, in 1813 and 1814. Take the first letter of the element's name: hydrogen is H, oxygen is O, carbon is C, nitrogen is N.

When that letter is already taken, add a second one. Calcium and chlorine both start with C, like carbon, so they become Ca and Cl. The first letter is always a capital and the second is always small, and that matters: Co, with a small o, is cobalt, a single element, but CO, with two capitals, means one carbon atom and one oxygen atom together.

Some symbols seem not to match their names at all. They come from Latin, the language scientists often wrote in back then: iron is Fe from ferrum, gold is Au from aurum, sodium is Na from natrium, copper is Cu from cuprum.

The names of the elements change from language to language, but the symbols don't. A chemist in Tokyo, one in Tehran and one in Mexico City all write Fe for iron, even though their own words for iron are completely different. The symbols are a small language that every chemist in the world can read.

Transcript

1. 0:00Chemists write every element in one or two letters.
2. 0:08Hydrogen is H, oxygen O, carbon C. When the letter is taken, add a small second one.
3. 0:16Co, with a small o, is cobalt. CO, two capitals, is a carbon atom and an oxygen atom.
4. 0:25Some come from Latin. Iron is Fe, from ferrum. Gold is Au, from aurum.
5. 0:34In Tokyo, Tehran or Mexico City, chemists write the same symbols.
6. 0:41A tiny language every chemist can read.