To describe how many atoms are touching each other in a group of coordinated atoms, the term of coordination number (CN) is used. The CN is the number of neighboring atoms that each atom has immediately surrounding it. If each atom touches six atoms in its own plane, plus three atoms above and below in adjacent planes, then the CN for these atoms would be 12. The number of nearest atoms is dependent on two factors: (1) the type of bonding, and (2) the relative size of the atoms or ions involved.