Types of Compounds
Ionic compounds are compounds composed of ions, charged particles that form when an atom (or group of atoms, in the case of polyatomic ions) gains or loses electrons.
A cation is a positively charged ionAn anion is a negatively charged ion.Covalent or molecular compounds form when elements share electrons in a covalent bond to form molecules. Molecular compounds are electrically neutral.
Ionic compounds are (usually) formed when a metal reacts with a nonmetal (or a polyatomic ion). Covalent compounds are formed when two nonmetals react with each other. Since hydrogen is a nonmetal, binary compounds containing hydrogen are also usually covalent compounds.
Metal + Nonmetal —> ionic compound (usually)Metal + Polyatomic ion —> ionic compound (usually)Nonmetal + Nonmetal —> covalent compound (usually)Hydrogen + Nonmetal —> covalent compound (usually)
Types of Ions:Main-Group Metals (Groups IA, IIA, and IIIA)
Group IA, IIA, and IIIA metals tend to form cations by losing all of their outermost (valence) electrons. The charge on the cation is the same as the group number. The cation is given the same name as the neutral metal atom.
Ions of Some Main-Group Metals (Groups IA - IIIA)
GroupElementCationIon nameIAHH+hydrogen ion LiLi+lithium ion NaNa+sodium ion KK+potassium ion CsCs+cesium ionIIAMgMg2+magnesium ion CaCa2+calcium ion SrSr2+strontium ion BaBa2+barium ionIIIAAlAl3+aluminum ion
