Solids with ionic bonding

Their structure depends on two factors:

  • the ratio between the number of positive and negative ions (electrical neutrality);

  • the relative size of anions (anion radius \(R_a\)) and cations (cation radius \(R_c\)).

In cases where cations and anions have (in absolute values) the same electrical charge (see diagram):

  • if \(R_c/R_a > 0,73\), the structure model is \(\ce{ClCs}\) (simple cubic),

  • if \(0,33 < R_c/R_a < 0,73\), the structure model is \(\ce{NaCl}\) (face-centred cubic),

  • if \(0,23 < R_c/R_a < 0,33\), the structure model is \(\ce{ZnS}\).

Typical crystal structures of ionic compounds | Philippe Lours, École des mines d'Albi-Carmaux, 2014. | Additional information...Information
Typical crystal structures of ionic compoundsInformation[2]