Why is the second ionisation energy of Bismuth greater than that of Antimony?
Why is the second ionisation energy of Bismuth greater than that of Antimony?
There is a very small increase in size from Sb to Bi due to completely filled f- orbitals in Bi. As we know that after removing one electron the size of cation further decreases. This decrease is higher for Bi as compare antimony. So, in case of Bi it needs more energy to remove 2nd and 3rd electron from cation. Therefore higher 2nd and 3rd ionization energies for Bi.
The 1st1st ionisation enthalpy of Bismuth(Bi) is less than that of Antimony(Sb).
While the 2nd2nd and 3rd3rdionisation enthalpy of Bismuth is more than Antimony’s.
The data is given below
- Ionisation Energy Bismuth(eV) Antimony(eV)
- I 7.289 8.64
- II 16.687 16.53
- III 25.559 25.30
But this denies the trend that we notice while observing ionisation enthalpy along groups.
According to the trend, from top to bottom the ionisation energy generally decreases because the atomic radius increases (due to addition of a new shell). Therefore the valence electron is present further away from the nucleus. Hence can easily leave the atom on gaining sufficient energy.
But another important factor to be considered is Shielding Effect. Due to shielding effect, each intermediate electron-filled shell shields the outer shells from the nuclear charge to some extent. Leading to a reduction in the effective nuclear charge felt by the electron clouds present in the outer shells.
But ‘d’ and ‘f’ orbitals show poor shielding effects.
The increase in size when we move from Sb(206 Å) to Bi(230 pm) is very small(24 pm). Due to completely filled f-orbitals in Bi, the effective nuclear charge on the valance electron in Bi is considerable.
When we remove an electron from an atom the cation size decreases. This decrease is more for Bi than Sb. Hence when we want to remove the next electron more energy is required by Bi+ compared to Sb+
Hence the 2nd and 3rd ionisation enthalpy of Bismuth is more than Antimony’s.
There is a very small increase in size from Sb to Bi due to completely filled f- orbitals in Bi. As we know that after removing one electron the size of cation further decreases. This decrease is higher for Bi as compare antimony. So, in case of Bi it needs more energy to remove 2nd and 3rd electron from cation. Therefore higher 2nd and 3rd ionization energies for Bi.
The 1st1st ionisation enthalpy of Bismuth(Bi) is less than that of Antimony(Sb).
While the 2nd2nd and 3rd3rdionisation enthalpy of Bismuth is more than Antimony’s.
The data is given below
- Ionisation Energy Bismuth(eV) Antimony(eV)
- I 7.289 8.64
- II 16.687 16.53
- III 25.559 25.30
But this denies the trend that we notice while observing ionisation enthalpy along groups.
According to the trend, from top to bottom the ionisation energy generally decreases because the atomic radius increases (due to addition of a new shell). Therefore the valence electron is present further away from the nucleus. Hence can easily leave the atom on gaining sufficient energy.
But another important factor to be considered is Shielding Effect. Due to shielding effect, each intermediate electron-filled shell shields the outer shells from the nuclear charge to some extent. Leading to a reduction in the effective nuclear charge felt by the electron clouds present in the outer shells.
But ‘d’ and ‘f’ orbitals show poor shielding effects.
The increase in size when we move from Sb(206 Å) to Bi(230 pm) is very small(24 pm). Due to completely filled f-orbitals in Bi, the effective nuclear charge on the valance electron in Bi is considerable.
When we remove an electron from an atom the cation size decreases. This decrease is more for Bi than Sb. Hence when we want to remove the next electron more energy is required by Bi+ compared to Sb+
Hence the 2nd and 3rd ionisation enthalpy of Bismuth is more than Antimony’s.
