Is water on the periodic table?
Is water on the periodic table? Water is not on the periodic table, because the periodic table lists chemical elements, and water is a compound.
Each water molecule (H2O) is made of two hydrogen atoms bonded to one oxygen atom, and both of those elements are on the table (hydrogen, atomic number 1, and oxygen, atomic number 8). The same rule explains why salt (sodium chloride, NaCl), carbon dioxide, methane, ammonia and sugar are not listed: they are compounds built from elements, and ions such as ammonium and cyanide are groups of atoms, not elements.
Mixtures and alloys such as air, steel (iron and carbon), brass (copper and zinc) and bronze (copper and tin) are not on it either. Diamond and graphite are different forms of the element carbon, so they appear under carbon (atomic number 6) instead of getting their own tile. For a different question, see “how to read the periodic table of elements”.
The table lists only the 118 known elements, each defined by its number of protons. The same logic answers many similar questions. For a different question, see “what is a family in a periodic table”.
Salt is not on the table, but its elements sodium and chlorine are. Sugar (sucrose, C12H22O11) contains carbon, hydrogen and oxygen.
Air is a mixture of mostly nitrogen and oxygen with argon and small amounts of other gases. Steel is an alloy of iron with a little carbon, bronze is mostly copper and tin, and brass is mostly copper and zinc. Diamond is the element carbon in a crystal structure, so there is no separate 'diamond' on the table, and the same goes for graphite, graphene and fullerenes, which are allotropes of carbon.
Water appears in chemistry through its two elements: hydrogen (1) in group 1 and oxygen (8) in group 16, so in a chemical formula you will see H and O. Remember that the table lists the building blocks, and compounds and mixtures are combinations of those blocks. To look up a compound, find its elements, then use their atomic masses to work out its molar mass.