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

To determine the correct orders among the given chemical properties of the elements B, Al, Ga, In, and Tl, let's analyze each property step-by-step:

1. Atomic Radius:
   The atomic radius generally increases down a group in the periodic table due to the addition of electron shells. Thus, the expected order should be: \(B<Al<Ga<In<Tl\). This order is correct.
2. Electronegativity:
   Electronegativity typically decreases as you move down a group because the distance between the nucleus and valence electrons increases. The order given is: \(Al<Ga<In<Tl<B\). For main group elements, Boron being the uppermost element should have the highest electronegativity among these. Thus, this order is incorrect.
3. Density:
   Density generally increases down the group for metals due to increasing atomic mass. However, given that there are exceptions due to the unique property of each element, the provided order: \(Tl<In<Ga<Al<B\) conflicts with expected trends and known data, making it incorrect.
4. 1st Ionisation Energy:
   Ionisation energy generally decreases down a group due to increasing atomic size. However, within the same group, exceptions can occur. The order given is: \(In<Al<Ga<Tl<B\). Boron has the highest ionisation energy as expected. This order is correct.

Based on the given options, the correct sequences are: B and D Only