Bonding
Oxidation Numbers - An elements position in the periodic table can help us figure out what charge the ion has that they form.
1A family (alkali metals). 1 valence electron, loses an electron to form a cathion with +1 charge.
11A family (alkaline metals). 2 valence electrons, loses two electrons to form a 2+ cathion.
111A family. 3 valence electrons, loses three electrons to form a 3+ cathion.
VA family. 5 valence electrons, gains three to form an anion with a 3- charge.
V1A family. 6 valence electrons, gains two to form an anion with a -2 charge.
V11A family (halogens). 7 valence electrons, gains one for form an anion of -1 charge.
Multiple oxidation states - Some transition metals have multiple oxidation states e.g tin 2 (sn2+) and tin 3 (sn3+).
Polyatomic Ions - A polyatomic ion is composed of two or more atoms.e.g Mercury Ion (Hg2 2+) shows two mercury atoms bonded together. The plus two shows each mercury cathion has a +1 charge.
Compounds which are ionically bonded are commonly known as salts. In sodium chloride, each sodium cation is surrounded by 6 chlorine anions and each chlorine anion is surrounded by 6 sodium cations.
Balancing Charges - To work out the formula of a non-metal and a metal reacting, put the atoms side by side with the metal on the left.
Magnesium for example has 3s2 in its outer shell. This means it must lose two valence electrons to become stable. As a result it will create a cation of +2.
Bromine’s end configuration is 4s2 3d10 4p5 (the 4’s only add upto 7) showing it has 7 valence electrons and needs to gain one to become stable. Once it gains one more atom, it will become a bromide anion with a -1 charge.
Since the magnesium has a +2 charge, it needs 2 bromide anions each with a single negative charge in order to be balanced. The end formula will be MgBr2.
The same can be used to work out polyatomic formulas.e.g the ammonium cation is NH4+ and the sulfide anion is S2-. Two positive ammonium ions are needed to balance the two negative charges on the sulfide ion resulting in (NH4)2S.
Naming Ionic compounds - Write the name of the metal first, then the non-metal and add an -ide ending to the non-metal. e.g lithium and sulfur becomes lithium sulfide.
