why does lithium show anomalous behaviour ?

Hi ,

Lithium shows anomalous behavior due to the following reasons:

1.  Extremely small size of lithium atom and its ion

2.  Greater polarizing power of lithium ion (Li⁺) due to its small size which results in covalent character in its compounds

3.  Least electropositive character and highest ionization enthalpy as compared to other alkali metals

Hope, this answers your question.

Best wishes!