The document outlines guidelines for writing chemical formulas for binary compounds, indicating that the element farther left in the periodic table is listed first, with specific rules for the placement of hydrogen. It distinguishes between molecular formulas, which display the exact number of atoms, and empirical formulas, which show the simplest whole-number ratio of the atoms. Examples include compounds like KCl and H2O to illustrate these rules.

1. Guidelines for Writing Chemical Formulas
for Binary Compounds
1. Except for Hydrogen, the element farther to the left in the
periodic table appears first. Ie: KCl, PCl3, Al2S3, and Fe3O4
2. If hydrogen is present, it appears last except when the other
element is from group 16 or 17. Ie: LiH, NH3, B2H6, CH4
H2O, HCl and HI
3. If both elements are from the same group, the lower one
appears first. Ie: SiC and BrF3

2. A molecular formula shows the exact number of
atoms of each element in the smallest unit of a
substance
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance
H2O
H2O
molecular empirical
C6H12O6 CH2O
O3 O
N2H4 NH2