As the title says, why do some element symbols contain a single letter while others contain two letters?

  • 9
    $\begingroup$ Would it be as simple as # Elements - # Letters in Alphabet > 0? So you need more letters per element if you want to abbreviate them all. $\endgroup$
    – Eljee
    Commented Apr 8, 2015 at 13:09
  • $\begingroup$ @Eljee I think that's the answer. $\endgroup$
    – Endy Sun
    Commented Apr 8, 2015 at 13:27
  • 10
    $\begingroup$ @Eljee - at the time people recognized there were elements, they already had names for a number of substances that were elements. Even without knowing how many elements there were they already had namespace collisions if they went with single letters. A lucky few elements got the prestigious single letters, the rest were left with two (and lets not mention those poor unnamed elements with 3!). An interesting clash of language, science, and nature... $\endgroup$
    – Jon Custer
    Commented Apr 8, 2015 at 13:46

1 Answer 1


There is a bit of history behind this.

In the website Development of the chemical symbols and the Periodic Table, it is stated that the Swedish chemist Berzelius updated Dalton's previous method. He established a protocol for the symbols, still in use today:

  1. In the class which I call metalloids, I shall employ the initial letter only, even when this letter is common to the metalloid and some metal.
  2. In the class of metals, I shall distinguish those that have the same initials with another metal, or a metalloid, by writing the first two letters of the word.
  3. If the first two letters be common to two metals, I shall, in that case, add to the initial letter the first consonant which they have not in common:

for example, S = sulphur, Si = silicium, Sb = stibium (antimony), Sn = stannum (tin), C = carbonicum, Co = cobaltum (cobalt), Cu = cuprum (copper), O = oxygen, Os = osmium, &c

The basis of the symbols are the Latin word for the elements.

A notes as what Berzellius was refering to when he used the term 'metalloid', from the Wikipedia page Origin and use of the term metalloid:

In 1811, Berzelius referred to nonmetallic elements as metalloids, in reference to their ability to form oxyanions.


  • $\begingroup$ Interesting, but by the time Berzelius made this rule the metals potassium (K), uranium (U), tungsten (W) and yttrium (Y) were all known. What happened, is there something I am missing? $\endgroup$ Commented Oct 27, 2020 at 19:12

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