How to input chemical compounds

LaTeX is an instrument for writing mathematical expressions. The "mchem" part of this instrument is for writing chemical formulas.

Chemical formulas to be displayed in a line of text, have to be enclosed in dollar signs and curly brackets \ce, tj. $ \ce{...} $

Chemical formulas to be displayed in a separate line have to be enclosed in double dollar signs $$ \ce{....} $$

for example:

Instructions for LaTeX users can be found on the internet: LaTeX math and equations , or LaTeX Wikibooks

Instructions for "mchem" users can be found here: LaTeX math and equations

See also instructions for writing mathematical formulas.
How to enter mathematical symbols in questions?