Among Sc, Mn, Co and Cu, identify the element with highest enthalpy of atomisation. The spin only magnetic moment value of that element in its +2 oxidation state is BM (in nearest integer).
Answer
4
Solution
Enthalpies of atomisation ( kJ mol-1, NCERT): Sc 326, Mn 281, Co 425, Cu 339.
Co has the highest enthalpy of atomisation (more unpaired electrons, stronger metallic bonding; Mn is low because of its stable half-filled 3d5 configuration).
Co2+: [Ar] 3d7
unpaired electrons n = 3
= n(n+2) = 3 5 = 15
= 3.87 BM 4 BM
Answer: 4