A chemical compound is a substance composed of 2+ chemical elements.

Types of Compounds

  • Binary
    • Binary compounds consist of only 2 elements
  • Ionic
    • Ionic compounds form lattices. They can't be separated into groups because there is no way of saying which specific atom another one is grouped with.
    • Overall charge of neutral, as a solid.
    • Steal electrons to balance out this charge, rather than sharing them
  • Covalent
    • Elements that are combined by covalent bonds share pairs of electrons between them to balance charge.

Writing Compounds

  • Label the amount of a substance if it's greater than 1, e.g. H2O
  • Use brackets if molecules have a grouped subscript, e.g. Ca(NO3)2.4H2O
  • Ionic Compounds
    • Binary
      • Cation, then Anion (Positive then Negative)
    • 3+
      • Cation, then Anion
      • “Water of crystallization” or other solvents that are present in the solid are written after the ionic formula with a full stop. e.g. Ca(NO3)2.4H2O
  • Covalent Compounds
    • Binary
      • The left-most (first), then top-most element goes first
      • Except that Hydrogen goes last (except with group 16 or 17)
        • e.g. NaOH vs HCl
    • 3+
      • Carbon, followed by Hydrogen, followed by remaining in alphabetical order
      • e.g. C2H6O, C4H9BrO

Naming Compounds (Nomenclature)

IUPAC have a systematic way of naming elements and compounds.
e.g. H20 = oxidane

See Naming Chemical Compounds for more details.