CHEM 1P00 Lecture Notes - Fall 2018 Lecture 8 - Dmitri Mendeleev, Acetic acid, Alkali metal
Document Summary
Recap: a compound is a substance composed of the atoms of two or more elements. The formula of a compound gives it composition in terms of the elements it contains. Rules for writing formulas: each atom is represented by its elemental symbol, the relative number of each type of atom is given a subscript. If the subscript of a give atom is 1, the subscript is omitted. Example (cid:1840)(cid:2870)(cid:1841)(cid:2872) two atoms of nitrogen and four atoms of oxygen. The order in which the elements are written in formulae depends on: the chemical nature of the element, the class of compounds it belongs to. Organic compounds: always contain carbon, usually contains hydrogen, sometimes contains other elements, are the largest class of compounds. For organic compounds, we always write: carbon first, hydrogen second, other elements in order of increasing atomic mass, oxygen last. Molecular formula: a molecular formula gives the actual numbers of each type of atom in a molecule.
