Colour and magnetic properties — NEET & JEE Questions

Question 1 · difficulty L1 · recall

A coordination compound is paramagnetic when it contains

• A. one or more unpaired electrons
• B. only paired electrons
• C. no electrons
• D. only closed-shell ligands

Question 2 · difficulty L2 · understanding

A complex with all electrons paired is

• A. paramagnetic
• B. diamagnetic
• C. ferromagnetic by definition
• D. necessarily coloured

Question 3 · difficulty L2 · understanding

The colour of many transition-metal complexes is commonly associated with

• A. absorption of visible light causing d-electron transitions
• B. nuclear transitions
• C. complete absence of d electrons
• D. emission of all visible wavelengths equally

Question 4 · difficulty L2 · understanding

A $d^0$ or $d^{10}$ complex is often colourless with respect to ordinary d-d transitions because

• A. there are no suitable partially occupied d levels for such transitions
• B. it contains no metal ion
• C. it absorbs all visible wavelengths equally
• D. all d orbitals have infinite energy

Question 5 · difficulty L3 · application

Which ion is expected to be diamagnetic?

• A. $Sc^{3+}$ ($d^0$)
• B. $Ti^{3+}$ ($d^1$)
• C. $Fe^{3+}$ ($d^5$)
• D. $Cu^{2+}$ ($d^9$)

Question 6 · difficulty L3 · application

How many unpaired electrons are present in a high-spin $d^5$ ion?

• A. 1
• B. 3
• C. 5
• D. 0

Question 7 · difficulty L3 · application

A complex has two unpaired electrons. Its spin-only magnetic moment is closest to which value? Use $\mu=\sqrt{n(n+2)}$ BM.

• A. 1.73 BM
• B. 2.83 BM
• C. 3.87 BM
• D. 5.92 BM

Question 8 · difficulty L3 · application

A coordination compound is experimentally diamagnetic. Which conclusion is directly supported?

• A. All its electrons are paired
• B. It must be colourless
• C. It contains no transition metal
• D. It must have oxidation state zero

Question 9 · difficulty L4 · application

A $d^6$ metal ion forms a strong-field octahedral complex in which electrons pair in the lower-energy set before occupying the higher-energy set. What magnetic behaviour is expected for the low-spin complex?

• A. Strongly paramagnetic with four unpaired electrons
• B. Diamagnetic
• C. Paramagnetic with five unpaired electrons
• D. Always ferromagnetic

Question 10 · difficulty L4 · application

A high-spin octahedral $d^6$ complex has how many unpaired electrons?

• A. 0
• B. 2
• C. 4
• D. 6