Question

The correct orders among the following are:  
[A.] Atomic radius : \(B<Al<Ga<In<Tl\) 
[B.] Electronegativity : \(Al<Ga<In<Tl<B\) 
[C.] Density : \(Tl<In<Ga<Al<B\) 
[D.] 1st Ionisation Energy : 
In\(<Al<Ga<Tl<B\) 
Choose the correct answer from the options given below :

• A. B and D Only
• B. A and C Only
• C. C and D Only
• D. A and B Only

Hint:

Remember the general trends in atomic radius, electronegativity, density, and ionization energy down a group in the periodic table. Be aware of anomalies, especially in the p-block elements, due to factors like d-electron shielding and electronic configurations. For Group 13, the trends often show irregularities involving Ga and In.

Answer 1

The Correct Option is A

Let's analyze the trends in Group 13 elements (Boron family) for the given properties: B, Al, Ga, In, Tl. Atomic Radius: Generally, atomic radius increases down a group due to the addition of new electron shells. 
However, there's an anomaly due to poor shielding by the d-electrons in Ga. 
The correct order is B<Al<Ga<In<Tl. Order A: B<Al<Ga<In<Tl (Correct) 
Electronegativity: Electronegativity generally decreases down a group due to increasing atomic size and shielding. However, due to the poor shielding by d-electrons in Ga and In, their electronegativities are slightly higher than expected. 
The general trend is B>Al>Ga \approx In>Tl. The given order is Al<Ga<In<Tl<B. Order B: Al<Ga<In<Tl<B (Correct) Density: Density generally increases down a group due to increasing atomic mass. However, the volume also plays a role. 
The order is B<Al<Ga<In<Tl. The given order is Tl<In<Ga<Al<B. Order C: Tl<In<Ga<Al<B (Incorrect, the density of Al is less than Ga) First Ionisation Energy: Ionisation energy generally decreases down a group due to increasing atomic size and shielding. However, there are irregularities due to the electronic configurations. 
The correct order is B>Al<Ga<Tl<In. The given order is In<Al<Ga<Tl<B. Order D: In<Al<Ga<Tl<B (Correct) From the analysis: Order A (Atomic radius) is correct. Order B (Electronegativity) is correct. Order C (Density) is incorrect. Order D (1st Ionisation Energy) is correct. 
The correct orders are B and D. Therefore, the correct option is (1).