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Naming Ionic Compounds - GOB Chemistry

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  • Order of ions in ionic formulas and names
    The cation (positive ion) is always listed first, followed by the anion (negative ion) in both formulas and names.
  • Naming main group cations
    Name the cation by the element name only, e.g., Na+ is 'sodium'. The charge is implicit and not stated.
  • Naming polyatomic cations
    Use the name of the polyatomic ion as given, e.g., NH4+ is 'ammonium'. The charge and formula are implicit.
  • IUPAC naming for transition metal cations
    Name the element plus the charge in Roman numerals in parentheses, e.g., Fe3+ is 'iron (III)'.
  • Classical naming for transition metal cations
    Use Latin-based names for different charges, e.g., Fe3+ is 'ferric', Fe2+ is 'ferrous'. This system is mostly used in medicine.
  • Exceptions where charge is not specified for transition metals
    Silver (Ag+) and zinc (Zn2+) only have one stable charge, so no charge is specified in their names.
  • Naming main group anions
    Name the element with an -ide suffix, e.g., O2- is 'oxide', Cl- is 'chloride'. The charge is implicit.
  • Naming polyatomic anions
    Use the name of the polyatomic ion as given, e.g., OH- is 'hydroxide'. The charge and formula are implicit.
  • General rule for naming ionic compounds
    Name the cation first, then the anion, separated by a space, e.g., K3N is 'potassium nitride'.
  • Naming K3N
    K+ is potassium, N3- is nitride, so the compound is named 'potassium nitride'.
  • Naming Cu(OH)2
    Cu2+ is copper (II) or cupric, OH- is hydroxide, so the compound is 'copper (II) hydroxide' or 'cupric hydroxide'.
  • Steps to determine ionic formula from compound name
    Identify symbols, determine cation and anion charges, then find the lowest ratio to balance charges to zero.
  • Formula for magnesium sulfate
    Mg2+ and SO42- charges balance 1:1, so formula is MgSO4.
  • Formula for copper (I) sulfite
    Cu+ and SO32- require 2 Cu+ ions per sulfite ion, formula is Cu2SO3.
  • Why specify charge for transition metals in names?
    Transition metals can have multiple charges, so the charge must be indicated to avoid ambiguity.
  • What suffix is used for main group anions?
    The suffix '-ide' is added to the element name to form the anion name.
  • What is implicit in the name of an ion?
    The fact that it is an ion and its charge are understood and do not need to be explicitly stated.
  • Difference between IUPAC and classical naming for transition metals
    IUPAC uses Roman numerals for charge; classical uses Latin-based names for different charges.
  • Why learn classical names if outdated?
    Classical names are still used in the medical community and on product labels.
  • How to name polyatomic ions in compounds
    Use the polyatomic ion's given name directly without adding 'ion' or charge.