When an element loses or gains electrons and forms an ion, the element is said to have a new oxidation state . Because carbon is positive, it is written on the left side of the formula, while oxygen is written on the right side of the formula, because it is negative. When the element is not combined with any other element, it always has 0 oxidation state. Type I and IV belong to the class of covalent compounds. Types II , III and V belong to the class of ionic compounds.
All salts are ionic compounds.
These formulas correspond to the molecular forms of the elements. That Contain a Metal and a Nonmetal. These are compounds formed by the combination of a metal and a non-metal. Remember that metals are located on the left side of the periodic table, while non-metals are located on the right side. Examples are NaCl, CaO, AlBr 3 .