MCQ Detailed View

In atomic chemistry, penetration effect refers to the extent to which an electron in a given orbital can approach the nucleus, experiencing less shielding from inner electrons. Orbitals with higher penetration spend more time closer to the nucleus, resulting in stronger electrostatic attraction between the nucleus and the electron.

Among the orbitals, s-orbitals have the maximum penetration effect. This is because the electron density of s-orbitals is highest near the nucleus. Even though p, d, and f orbitals may have radial nodes and angular lobes, s-orbitals have a spherical shape that allows their electrons to get very close to the nucleus. As a result, s-electrons are less shielded by other electrons, contributing to lower energy levels and stronger nuclear attraction compared to electrons in p, d, or f orbitals of the same principal quantum number.

The penetration effect directly influences the energy ordering of orbitals. For instance, in multi-electron atoms, the (n+ℓ) rule shows that orbitals with higher penetration (like s-orbitals) have lower energy than orbitals with the same principal quantum number but less penetration (like p, d, or f). This explains why the 4s orbital is filled before the 3d orbital.

Comparing orbitals:

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  s-orbitals: Maximum penetration, spherical shape, electrons closest to nucleus.

  
  


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  p-orbitals: Less penetration, dumbbell-shaped, partially shielded.

  
  


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  d-orbitals: Even less penetration, more complex shape.

  
  


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  f-orbitals: Lowest penetration, highly diffuse electron density, strongly shielded.

  
  

Understanding penetration effects is crucial in inorganic chemistry for predicting atomic sizes, ionization energies, chemical reactivity, and the arrangement of electrons in multi-electron atoms.

Therefore, among the given options, the s-orbital has the maximum penetration effect.