Ionic Bonding

Ionic Bonding

  • Ionic bonding forms when one atom donates an electron to another atom, resulting in both atoms having full outer electron shells. This is called an electron transfer.

  • In an ionic bond, a metal atom donates an electron to a non-metal atom. The metal becomes a positive ion (cation) and the non-metal becomes a negative ion (anion).

  • The metal and non-metal ions are attracted to each other due to their opposite charges. This electrostatic attraction is known as an ionic bond.

Dot and Cross Diagrams

  • Dot and cross diagrams represent ionic bonding by showing the outer shell electrons of atoms. You can use these to help understand and explain the process of ionic bonding.

  • In a dot and cross diagram, a dot represents an electron from one atom, while a cross represents an electron from the other atom.

  • For example: sodium chloride (NaCl) has one electron in the outer shell of sodium (Na). Chlorine (Cl) has seven electrons in its outer shell. Sodium donates its outer shell electron to Chlorine, forming positive Sodium ions and negative Chloride ions. The ionic bond is the attraction between these oppositely charged ions.

Properties of Ionic Compounds

  • Ionic compounds (such as Sodium Chloride – NaCl) have high melting and boiling points due to the strong ionic bonds.

  • The structure of ionic compounds is a giant ionic lattice. It’s a repeating pattern of positive and negative ions.

  • When in a liquid or aqueous state, ionic compounds can conduct electricity. The ions are free to move and carry charge.

  • Ionic compounds are often soluble in water. In water, the ions separate and are free to move, allowing the solution to conduct electricity.

Predicting Ionic Charges

  • The ion charges can be predicted by knowing the number of electrons the atom needs to lose or gain to achieve a full outer shell.

  • Group 1 elements (like Sodium) form +1 ions, Group 2 elements (like Magnesium) form +2 ions, and Group 6 elements (like Oxygen) form -2 ions. Similarly, Group 7 elements (like Chlorine) form -1 ions.

  • Transition metals (elements from groups 3-12 in the periodic table) often have more than one possible charge. Iron, for example, can form +2 or +3 ions.

  • It’s essential to appreciate that ionic charges must balance. The positive and negative charges in an ionic compound should equal zero. For example, for aluminium chloride (AlCl₃), the charges balance because aluminium ions are +3 and chloride ions are -1.