Question

In comparison to boron, berylium has :

• A. lesser nuclear charge and greater first ionisation enthalpy
• B. lesser nuclear charge and lesser first ionisation enthalpy
• C. greater nuclear charge and greater first ionisation enthalpy
• D. greater nuclear charge and lesser first ionisation enthalpy

Answer 1

The Correct Option is A

To solve the question, we need to compare the atomic properties of beryllium and boron in terms of nuclear charge and first ionisation enthalpy.

1. Nuclear Charge: Nuclear charge is equivalent to the atomic number of an element, which is the number of protons in the nucleus.
   • Beryllium (Be) has an atomic number of 4.
   • Boron (B) has an atomic number of 5.
   Thus, boron has a greater nuclear charge than beryllium.
2. First Ionisation Enthalpy: The first ionisation enthalpy is the energy required to remove the outermost electron from a neutral atom in its gaseous state.
   • Beryllium has a completely filled 2s orbital, giving it extra stability. Therefore, it requires more energy to remove an electron compared to boron.
   • Boron has one electron in the 2p subshell, which is easier to remove due to higher energy than 2s electrons.
   Hence, beryllium has a greater first ionisation enthalpy than boron.

Based on these properties, in comparison to boron, beryllium has a lesser nuclear charge because it has fewer protons. However, beryllium has a greater first ionisation enthalpy due to its filled 2s orbital configuration making its electrons harder to remove.

Therefore, the correct answer is: lesser nuclear charge and greater first ionisation enthalpy.