What Is Valence or Valency?

What Is Valence or Valency?

Valence is a measure of how readily an atom or radical forms a bond.
Valence is a measure of how readily an atom or radical forms a bond. Jason Reed, Getty Images

The words valence and valency have two related meanings in chemistry.

  • Valence describes how easily an atom or radical can combine with other chemical species. This is determined based on the number of electrons that would be added, lost or share if it reacts with other atoms.
  • Valence is denoted using a positive or negative integer used to represent this binding capacity. For example, common valences of copper are 1 and 2.

    Table of Element Valences

    Number Element Valence
    1Hydrogen(-1), +1
    2Helium0
    3Lithium+1
    4Beryllium+2
    5Boron-3, +3
    6Carbon(+2), +4
    7Nitrogen-3, -2, -1, (+1), +2, +3, +4, +5
    8Oxygen-2
    9Fluorine-1, (+1)
    10Neon0
    11Sodium+1
    12Magnesium+2
    13Aluminum+3
    14Silicon-4, (+2), +4
    15Phosphorus-3, +1, +3, +5
    16Sulfur-2, +2, +4, +6
    17Chlorine-1, +1, (+2), +3, (+4), +5, +7
    18Argon0
    19Potassium+1
    20Calcium+2
    21Scandium+3
    22Titanium+2, +3, +4
    23Vanadium+2, +3, +4, +5
    24Chromium+2, +3, +6
    25Manganese+2, (+3), +4, (+6), +7
    26Iron+2, +3, (+4), (+6)
    27Cobalt+2, +3, (+4)
    28Nickel(+1), +2, (+3), (+4)
    29Copper+1, +2, (+3)
    30Zinc+2
    31Gallium(+2). +3
    32Germanium-4, +2, +4
    33Arsenic-3, (+2), +3, +5
    34Selenium-2, (+2), +4, +6
    35Bromine-1, +1, (+3), (+4), +5
    36Krypton0
    37Rubidium+1
    38Strontium+2
    39Yttrium+3
    40Zirconium(+2), (+3), +4
    41Niobium(+2), +3, (+4), +5
    42Molybdenum(+2), +3, (+4), (+5), +6
    43Technetium+6
    44Ruthenium(+2), +3, +4, (+6), (+7), +8
    45Rhodium(+2), (+3), +4, (+6)
    46Palladium+2, +4, (+6)
    47Silver+1, (+2), (+3)
    48Cadmium(+1), +2
    49Indium(+1), (+2), +3
    50Tin+2, +4
    51Antimony-3, +3, (+4), +5
    52Tellurium-2, (+2), +4, +6
    53Iodine-1, +1, (+3), (+4), +5, +7
    54Xenon0
    55Cesium+1
    56Barium+2
    57Lanthanum+3
    58Cerium+3, +4
    59Praseodymium+3
    60Neodymium+3, +4
    61Promethium+3
    62Samarium(+2), +3
    63Europium(+2), +3
    64Gadolinium+3
    65Terbium+3, +4
    66Dysprosium+3
    67Holmium+3
    68Erbium+3
    69Thulium(+2), +3
    70Ytterbium(+2), +3
    71Lutetium+3
    72Hafnium+4
    73Tantalum(+3), (+4), +5
    74Tungsten(+2), (+3), (+4), (+5), +6
    75Rhenium(-1), (+1), +2, (+3), +4, (+5), +6, +7
    76Osmium(+2), +3, +4, +6, +8
    77Iridium(+1), (+2), +3, +4, +6
    78Platinum(+1), +2, (+3), +4, +6
    79Gold+1, (+2), +3
    80Mercury+1, +2
    81Thallium+1, (+2), +3
    82Lead+2, +4
    83Bismuth(-3), (+2), +3, (+4), (+5)
    84Polonium(-2), +2, +4, (+6)
    85Astatine?
    86Radon0
    87Francium?
    88Radium+2
    89Actinium+3
    90Thorium+4
    91Protactinium+5
    92Uranium(+2), +3, +4, (+5), +6