a). Explain the reason for the variation of the first ionization energies of the third period elements.
Ionization energy is the amount of energy required to remove an electron from neutral gaseous electrons.
Across period, in a periodic table from left to right ionization energy should increase.
Third period elements are:
Na, Mg, Al, Si, P, S , Cl, Ar
Order of ionization energy in third period:
In third period element with highest ionization energy is argon due to stable octet configuration.
Mg has more ionization energy than Al.
due too its stable ns2 configuration of Mg.
P has more ionization energy than sulphur (S) a because phosphorous has half filled p sub shell in its valence shell that gives extra stability and hence more energy is required to remove the electron.