Given below are two statements :
Statement (I) : The first ionisation enthalpy of group 14 elements is higher than the corresponding elements of group 13.
Statement (II) : Melting points and boiling points of group 13 elements are in general much higher than those of corresponding elements of group 14.
In the light of the above statements, choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Go across one group in the same period: the nucleus pulls harder, and bonding gets stronger too.

1. Statement I. A group 14 element has one more proton than its group 13 neighbour, and the extra electron goes into the same shell. So the effective nuclear charge is higher and the atom is smaller, which makes the outer electron harder to remove. Statement I is correct.
2. Statement II. Group 14 elements have four valence electrons, and C, Si and Ge form giant covalent networks with four strong bonds per atom. Group 13 atoms have only three valence electrons and bond more weakly, so their melting and boiling points are lower, not higher. Statement II is incorrect.

   Pair (13 vs 14)	Δᵢ H₁ in kJ mol⁻¹	Melting point in K
   B vs C	801 vs 1086	2453 vs about 4373
   Al vs Si	577 vs 786	933 vs 1693
   Ga vs Ge	579 vs 761	303 vs 1218
   In vs Sn	558 vs 708	430 vs 505
   Tl vs Pb	589 vs 715	576 vs 600

3. So. In every pair the group 14 element is higher in both ionisation enthalpy and melting point. Statement I is correct and Statement II is incorrect, which is option (a).

The idea to keep. From group 13 to group 14 in a period, higher Z_(eff) raises the ionisation enthalpy, and four valence electrons give stronger bonding, so melting points rise too.

Answer from the NTA final answer key. Solution by PrepWiser.