Magnetic Properties, Interstitial Compounds, Alloy Formation

Magnetic properties:
(i) Metals and ions having unpaired electrons are paramagnetic and feel slight increase in weight in magnetic field.
(ii) Magnetic moment μ=\sqrt{n(n+2)} B.M for n unpaired electrons.
(iii) Fe, Co, Ni are used for making permanent magnets. These are ferromagnetic in nature.
(iv) Zn²⁺, Sc³⁺, Cu⁺ etc do not have unpaired electrons and are diamagnetic and they feel weak repulsion in magnetic field.
(v) Cr has magnetic moment 6.93 B.M due to 6 unpaired electrons in ground state. In +2 oxidation state Mn⁺² has 5.96 B.M magnetic moment. These are highest values in 3d series.

Interstitial compounds:
(i) H, C, B and N atoms enter in interstitial space of elements of d-block to form non stoichiometric compounds also known as interstitial compounds.
(ii) These are chemically inert.
(iii) These retain metallic conductivity, have higher hardness higher melting point but lower ductility and malleability than the pure metals.
(iv) There is no bond between metal and the above non metals

Reactivity: Elements of d-block are much less reactive than elements of s and p-blocks because of high ionization energy, low heat of hydration, high heat of sublimation. Pt, Pd, Rh and Au are noble metals.

Alloy formation:
(i) Due to very close atomic sizes; elements of d-block easily form alloys. Alloys of Hg are called amalgams. Li, Fe, Pt, do not form amalgams.
(ii) Alloy formation makes metals hard, rust proof, high melting and high boiling points.
(iii) Oxidation state of metal in alloy is "zero"

Complex formation:
(i) Because of high charge; size ratio and vacant-d-orbitals, metals and ions of d-block easily form complexes.
(ii) Complexes of actinoids are more stable. They can use 5f orbitals for complex formation while lanthanoids can not use 4f orbitals.