ABG 7

ABG 7

1. FIRST IONISATION ENERGY

   • The energy required to remove one electron from every atom in a mole of gaseous atoms of an element X(g) --> X+(g) + e-

2. successive ionisation energies

   • second ionisation energy
     • the energy required to remove one electron from every ion a mole of gaseous X+ ions
   • Third Ionisation energy
     • is the energy required to remove one electron from every ion in a mole of gaseous X2+ ions
   • fourth ionisation energy
     • X3+(g) --> X4+(g) + e

3. Ionisation energies are influenced by four factors:

   • greater the nuclear charge the greater the ionisation energy
   • the more electron shielding the smaller the ionisation energy
   • the greater the distance of the outermost electron from the nucleus the smaller the ionisation energy
   • the greater the attraction between the outermost electron and the nucleus the greater the ionisation energy

4. successive ionisation energies increase because:

   • nuclear charge remains constant but there are fewer electrons
   • distance between outermost electrons and the nucleus becomes smaller
   • greater attraction between outermost electrons and nucleus

5. There is a general increase in first ionisation energy across a Periods 2 and 3

   • increasing nuclear charge
   • no increase in number of shielding shells
   • decrease in the distance from the outermost electron to the nucleus

6. There is a decrease in the first ionisation energy down a group:

   • increase in nuclear charge
   • distance between outermost electrons and nucleus increases
   • number of shielding shells increase
   • Increasing attraction between outermost electron and the nucleus

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