Determine ion charge

[Kassandra Javier 2D]

How do you determine the charge of an ion when trying to generate the formula of a compound? For example, question E.15 asks for the molar mass of a sulfide of the given metal, but how do you know the charge of the metal and the charge of sulfur and other elements?

[Chem_Mod]

The example given is M(OH)2. OH has a charge of -1 and the compound is neutral, so M must have a +2 charge. Therefore, since S also has a -2 charge, the formula for the metal sulfide is MS.

[Maeve Settle 2B]

Hi! The periodic table is actually super useful in determining the charge of a single ion. In columns 1, 2, and 13 the charge of those ions will be +1, +2, and +3. In columns 15, 16, and 17 the charges will be -3, -2, and -1. Remembering the column number and corresponding charge will be super handy when you need to determine singular ion charge. When you're working with polyatomic ions, like OH-, it's useful to memorize their charge so you can complete problems quickly. Hope this helps!

[Vikram Sharma]

Elements will always try to fill their valence shell following the octet rule, so you can determine an ion's charge based on how many electrons it either has to gain or lose to achieve a full valence shell (8 electrons). If it loses electrons, the ion will be a cation (positive), and if it gains electrons it will be an anion (negative),