1. In the Pt group, lithium differs in many aspects from its own family elements. Similarly, in the 2rd group, beryllium differs in many aspects from its own family.
2. For example, lithium forms compounds with more covalent character. But other alkali metals of this group form only ionic compounds.
3. Similarly, beryllium forms compounds with more covalent character while the other elements of this family form only ionic compounds.
4. Lithium and beryllium resemble more with the elements lying at their right-hand side in the 3t1 period than with the other members of their own family.
5. These kinds of anomalies are also observed from 13th to 17th groups.
6. This sort of similarity is commonly referred to as diagonal relationship in the periodic properties.
7. The anomalous behaviors are attributed to the following factors:
- Smaller atomic size
- Higher ionization enthalpy
- High electronegativity
