CHEMISTRY COMMUNITY

How do you find the chemical formula of compounds?

For example, chronium(III) and manganese(II)

Section D in fundamentals goes over how to derive the chemical formula from a compound's name.

Hi!

You usually will not have to find a chemical formula without any given values. Metals, gases, etc. have different characteristics that make them easier to figure out; which is listed in the book.

Hope this helped.

The Roman numerals refer to the charge on that atom. In this case, chromium has a +3 charge so you know how to write the formula for a neutral molecule.

Hi! In addition to what others have mentioned above, it's helpful to know the charges of the common elements on the table. For example, Group I all has a +1 charge, Group II has +2, etc. Once you know the charges of the elements in your compound, you can find out how many atoms of an element are in it. (Ex. Copper (II) Chloride --> Copper has +2 charge, chloride has -1 charge, the molecule has a net charge of 0, so there must be 2 chlorides --> CuCl2 ).

The chemical formula of compounds can be created using rules that can be generalized used on patterns. These rules can be found in the fundamentals part of the textbook (section D). The two things you ask of, however, are cations and perhaps you mean to ask how to find the charges for them. For transition metals, the roman numeral will be the charge. Hope this helps!