Moderate

Which will need maximum energy to remove its one electron?

Correct answer: C. K+➔ K++ +e-

  • A. Na ➔ Na+ + e-
  • B. Ca+➔ Ca++ +e-
  • C. K+➔ K++ +e-
  • D. C2+➔ C3+ + e-

Explanation

In all options except C, the electron being removed is from the outer most (valence) shell and hence the shielding is greatest, hence electron affinity is low. However, when a second electron is removed from potassium, it is taken from an inner shell which faces a high effective nuclear charge and low shielding, hence the electron affinity is very high.

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Chemical bonding explains molecular shape through VSEPR theory and distinguishes sigma bonds from pi bonds. Questions involve hybridization, bond angles, dipole moment and bond energy, including how electron-pair repulsion determines geometry and how bond polarity differs from the overall polarity of a molecule.

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