Did you know? Chemical elements are pure chemical substances made up of a single type of atom (eg oxygen, carbon, mercury, gold).
The periodic table lists 118 named elements, and more are being added as researchers synthesise new ones. Each chemical element is denoted by a symbol, which is either the first letter or a combination of the first letter and another letter from the element’s name, in English (eg carbon is C, calcium is Ca, argon is Ar, arsenic is As), or in Greek or Latin (eg gold is Au from the Latin aurum; mercury is Hg from the Greek-derived word hydrargyrum).
Write the names of chemical elements in roman type without a capital, but use an initial capital for the symbols:
calcium (Ca) carbon (C) helium (He) oxygen (O)
Some synthetic elements are named after people; however, unlike other eponymic names (such as disease names), they are written without a capital:
lawrencium (Lr) meitnerium (Mt)
In the periodic table, elements are listed by group (columns), period (rows), blocks (s, p, d, f) and unique numbers. Use lower case for all terms associated with the table, and hyphenate block names:
Calcium is element 20 in group 2, period 4 and s-block of the periodic table.
In general texts, it is best to write out chemical element names in full, wherever possible (eg sulfur, carbon); however, in technical reports and scientific journal papers, it might be appropriate to use the symbol (especially in tables and figures). If abbreviations for chemical elements are used, consider identifying them in full at first use in text or in notes under tables and figures:
phosphorus (P) silver (Ag)
