Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 B.M. and that of Co2+ is 4.87 B.M. Why?
The electronic configuration of
Cr3+ - [Ar] 3d3
Co2+- [Ar] 3d7
Cr3+ has a symmetrical electron distribution and will only have spin magnetic moment contribution whereas Co2+ has no symmetrical distribution of electrons so it will have orbital magnetic moment and spin magnetic moment contribution. Therefore, the total magnetic moment for Co2+ will be higher than Cr3+.
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Mention the type of compounds formed when small atoms like H, C and N gettrapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.Chemistry - Exemplar
(a) Answer the following questions :
(i) Which element of the first transition series has highest second ionization enthalpy?
(ii) Which element of the first transition series has highest third ionization enthalpy?
(iii) Which element of the first transition series has lowest enthalpy of atomisation?
(b) Identify the metal and justify your answer.
(i) Carbonyl M (CO)5
Chemistry - Exemplar
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl solution, orange crystals of compound (D) crystallise out. Identify compounds A to D and also explain the reactions.
An oxide of mangnese (A) is fused with KOH in the presence of an oxidizing agent and dissolved in water. A dark green solution of compound (B) is obtained. Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). Alkaline solution of (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
Chemistry - Exemplar