Skip to main content
Medicine LibreTexts

1.05: Ionizations

  • Page ID
  • When some atoms dissolve in water they become charged particles called ions. Some become positively charged ions and others negatively charged. Ions may have one, two or sometimes three charges. The table below shows examples of positively and negatively charged ions with the number of their charges.

    Positive Ions Negative Ions
    H+ Hydrogen Cl- Chloride
    Ca2+ Calcium OH- Hydroxyl
    Na+ Sodium HCO3- Bicarbonate
    K+ Potassium CO32- Carbonate
    Mg2+ Magnesium SO42- Sulfate
    Fe2+ Iron (ferrous) PO43- Phosphate
    Fe3+ Iron (ferric) S2- Sulfide

    Positive and negative ions attract one another to hold compounds together. Ions are important in cells because they conduct electricity when dissolved in water. Substances that ionize in this way are known as electrolytes. The molecules in an animal’s body fall into two groups: inorganic compounds and organic compounds. The difference between these is that the first type does not contain carbon and the second type does.


    • Ruth Lawson (Otago Polytechnic; Dunedin, New Zealand)