horizontal rows of periodic table
vertical columns of periodic table
those in the same group have similar physical and chemical properties
two or more atoms tightly bound together. These atoms behave in their own distinct way and are recognized as a single object, not two.
Example: 02
molecular compounds
compounds composed of molecules that contain more than one type of atom.
Example: H2O
molecular formulas
chemical formulas that indicate the actual numbers and types of atoms in a molecule
Ex. H2O2
empirical formula
chemical formulas that give the smallest whole number ratios of the atoms in a molecule.
Ex. HO
If you know the molecular formula, you can find the empirical formula. However, if you have the empirical formula, you cannot determine the molecular formula.