Determining the Charge of Ions

Jun 28, 2024

Determining the Charge of Ions

Monoatomic Ions

  • Alkali Metals (Group 1A): Hydrogen, Lithium, Sodium, Potassium, Rubidium

    • Neutral as pure elements
    • Become ions acquire a +1 charge (except Hydrogen)

  • Alkaline Earth Metals (Group 2A): Beryllium, Magnesium, Calcium, Strontium

    • 2 valence electrons
    • Usually form ions with a +2 charge

Transition Metals

  • Usually have multiple oxidation states (discussed later)

Group 3A / Group 13 Elements

  • Elements: Boron, Aluminum, Gallium, Indium, Thallium
    • Typically have 3 valence electrons
    • Form ions with a +3 charge or sometimes a +1 charge

Electron Configuration Example

  • Aluminum (Al): 1s2 2s2 2p6 3s2 3p1
    • 3 valence electrons
    • Forms a +3 charge upon losing 3 electrons

Group 4A / Group 14 Elements

  • Elements: Carbon, Silicon, Germanium, Tin, Lead
    • Can form +4 or sometimes +2 charge
    • Example: Silicon - 1s2 2s2 2p6 3s2 3p2

Group 5A / Group 15 Elements

  • Elements: Nitrogen, Phosphorus, Arsenic (metalloid)
    • Non-metals (N, P)
    • Form a -3 charge by gaining 3 electrons

Group 6A / Group 16 Elements

  • Elements: Oxygen, Sulfur, Selenium
    • Form a -2 charge by gaining 2 electrons

Group 7A / Group 17 Elements (Halogens)

  • Elements: Fluorine, Chlorine, Bromine, Iodine
    • Form a -1 charge by gaining 1 electron

Calculating Ion Charge

  • Formula: Difference between number of protons and number of electrons
  • Example: Aluminum (Al)
    • Atomic number: 13 (13 protons)
    • Loses 3 electrons: 13 protons - 10 electrons = +3 charge
  • Example: Oxygen (O)
    • Atomic number: 8 (8 protons)
    • Gains 2 electrons: 8 protons - 10 electrons = -2 charge

Transition Metals and Oxidation States

  • Copper (Cu): +1, +2
  • Iron (Fe): +2, +3
  • Cobalt (Co): +2, +3
  • Chromium (Cr): +2, +3
  • Silver (Ag): +1
  • Gold (Au): +1, +3

Polyatomic Ions

  • Memorize common ions
  • Examples:
    • Sulfate (SO4^2-)
    • Nitrate (NO3^-)
    • Ammonium (NH4^+)

Determining Charge Involving Hydrogen

  • Adding hydrogen to negative ions
  • Example: Adding H+ to SO3^2- (Sulfite) forms HSO3^- (Hydrogen Sulfite)

Summary

  • Metals form positive ions (cations) by losing electrons
  • Nonmetals form negative ions (anions) by gaining electrons
  • Ion charge determined by difference in protons and electrons
  • Understand and memorize common oxidation states and polyatomic ions