2.4 (a) Cite two important quantum-mechanical concepts associated with the Bohr model of the atom.
. (b) Cite two important additional reﬁnements that resulted ﬁ‘om the wave—mechanical atomic model.
(a) Two important quantum-mechanical concepts associat
2.17 The net potential energy EN between two adjacent ions is sometimes represented by the expression
EN =—2 + Déxp[—i] (2.12)
in which r is the interionic separation and C, D, and p are constants whose values depend on the specific material.