Atoms are electrically neutral because the number of protons is equal to the number of electrons and the electron and proton have equal and opposite charges.If an atom or molecule loses an electron it becomes positively charged. If an atom or molecule gains an electron it becomes negatively charged.Ionic bonds are formed when an atom donates an electron to another atom and becomes a positively charged ion. The other atom becomes a negatively charged ion.An ionic bond is the electrostatic attraction between oppositely charged ions.Ions in solution are called electrolytes.
| Ion | Function |
| calcium ions Ca2+ | nerve impulse transmission muscle contraction |
| magnesium ions Mg2+ | chlorophyll |
| sodium ions Na+ | nerve impulse transmission kidney function |
| potassium ions K+ | nerve impulse transmission stomatal opening |
| hydrogen ions H+ | catalysis of reactions pH determination |
| ammonium ions NH4+ | production of nitrate ions by bacteria |
| nitrate ions NO3- | nitrogen for amino acid and proteins |
| hydrogen carbonate ions HCO3- | maintains blood pH |
| Chloride ions Cl- | balances positive charges in cells |
| phosphate ions PO43- | cell membrane, nucleic acid and bone formation |
| hydroxide ions OH- | catalysis pH balance |