Question

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 the corresponding elements of group 14. Choose the most appropriate answer from the options given below:

• A. Statement I is correct but Statement II is incorrect
• B. Statement I is incorrect but Statement II is correct
• C. Both Statement I and Statement II are incorrect
• D. Both Statement I and Statement II are correct

Hint:

Ionisation enthalpy increases across a period as the nuclear charge increases, but the melting and boiling points of the elements generally follow the trends in atomic size and bonding strength.

Answer 1

The Correct Option is A

The question involves two statements about the properties of elements in Group 13 and Group 14 of the periodic table. Let's analyze each statement individually to determine their correctness and to substantiate the given answer.

1. Statement I: The first ionisation enthalpy of group 14 elements is higher than the corresponding elements of group 13.
   • Ionisation enthalpy is the energy required to remove the outermost electron from an atom in its gaseous state. It is influenced by atomic size, nuclear charge, and electronic configuration.
   • Group 14 elements (e.g., Carbon, Silicon) have more protons and a greater effective nuclear charge compared to Group 13 elements (e.g., Boron, Aluminium) for the same period, leading to a higher effective hold on their valence electrons. This results in higher ionisation enthalpy.
   • Therefore, the first ionisation enthalpy of Group 14 elements is indeed higher than that of Group 13 elements. Statement I is correct.
2. Statement II: Melting points and boiling points of group 13 elements are in general much higher than those of the corresponding elements of group 14.
   • The melting and boiling points are determined by the type of bonding and structure of the elements.
   • Group 14 elements typically have a covalent network structure, which usually leads to higher melting and boiling points (as seen in Carbon (diamond) and Silicon) compared to metallic bonding in Group 13 elements.
   • For example, Carbon in the form of diamond has one of the highest melting points, much higher than Boron or Aluminium.
   • Thus, generally, the melting and boiling points of Group 14 elements are higher compared to those in Group 13. Statement II is incorrect.

Based on our analysis, we conclude: Statement I is correct but Statement II is incorrect. Hence, the correct option is:

Statement I is correct but Statement II is incorrect

Answer 2

Statement I:
The first ionisation enthalpy of group 14 elements is indeed higher than that of group 13 elements, as the number of valence electrons increases from group 13 to 14, leading to a higher ionisation energy. 
Thus, Statement I is correct
Statement II: This statement is incorrect. 
The melting points and boiling points of group 13 elements are generally lower than those of group 14 elements due to the stronger metallic bonding in group 14 elements. 
Thus, Statement II is incorrect. 
Therefore, the correct answer is (1).