In comparison to boron, beryllium has:

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JEE Mains Previous Paper 1 (Held On: 12 Apr 2019 Shift 2)
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  1. Lesser nuclear charge and lesser first ionization enthalpy.
  2. Greater nuclear charge and lesser first ionization enthalpy
  3. Greater nuclear charge and greater first ionization enthalpy
  4. Lesser nuclear charge and greater first ionization enthalpy

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Option 4 : Lesser nuclear charge and greater first ionization enthalpy
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JEE Main 04 April 2024 Shift 1
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Concept:

  • Nuclear charge: The nuclear charge is the total charge of all the protons in the nucleus.

Nuclear charge of Boron (B) > Nuclear charge of Be

First ionization enthalpy:

Be = 1s2 2s2 (more stable)

B = 1s2 2s2 2p1

The first ionization of Beryllium is greater than that of boron because beryllium has a stable complete electronic configuration (1s2 2s2) so it requires more energy to remove the first electron from it. Whereas boron has the electronic configuration 1s2 2s2 2p1 which needs lesser energy than that of beryllium to remove the valence electron.

Ionisation energy of Be is greater than B due to ns2 outer electronic configuration.

The ionization energy is the energy required to remove an electron from its orbital around an atom to a point where it is no longer associated with that atom. The ionization energy of an element increases as one moves across the period in the periodic table because the electron is held tighter by the higher effective nuclear charge.
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