The first ionisation energies of magnesium and aluminium are respectively given by

The first ionisation energies of magnesium and aluminium are respectively given by
  1. 7.64, 5.98
  2. 7.64, 7.64
  3. 5.98, 7.64
  4. 5.98, 5.98

Solution

IE of Mg>IE of Al
Electronic configuration of
Mg=1s2,2s2,2p2,3s2
Al=1s2,2s2,2p6,3s2,3p1
Mg has stable configuration (fulfilled) than Al so removal of an electron is difficult hence, required more energy i.e. more ionisation energy.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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