The first ionization enthalpy values (in `kJ mol^(-1)`) of group 13 elements are:
`{:(B,Al,Ga,In,Ti),(801,577,579,558,589):}`
How do you explain this deviation from the general trend?

Explanation

The given IE, values (in KJ/mole) of group 13 are as follow
`{:(B,Al,Ga,In,Tl),(801,577,579,558,589):}`
`rarr` In genaral in a group IE values decrease down a group but from the above values we observe that there is no smooth decrease down the group.
`rarr` The decrease from B to Al is due to increase of size.
`rarr` The observed discontinuity in the IE values of Al and Ga, and between ln and Ga, and between Ln and Tl are due to inability of d- and f-electrons, which have low screening effect to compensate the increase in nuclear charge.