Reason for Lithium having a greater tendency to form covalent compounds than other elements in the group:

1. Atomic and Ionic Radii:
- Lithium is the smallest element in its group, and as we move down the group, the atomic and ionic radii increase.
- The larger atomic and ionic radii of the other elements make it easier for them to lose electrons and form ionic bonds, rather than sharing electrons in covalent bonds.

2. Electronegativity:
- Electronegativity is the measure of an atom's ability to attract electrons towards itself in a chemical bond.
- Lithium has a lower electronegativity compared to other elements in its group.
- The lower electronegativity of lithium indicates that it is less likely to attract electrons towards itself, making it more willing to share electrons in covalent bonds.

3. Ionization Energy:
- Ionization energy is the energy required to remove an electron from an atom or ion.
- Lithium has a lower ionization energy compared to other elements in its group.
- The lower ionization energy of lithium means that it requires less energy to remove an electron, making it more likely to participate in covalent bonding where electrons are shared, rather than losing electrons to form ionic bonds.

4. Polarizability:
- Polarizability is the ability of an atom or ion to induce a dipole in its neighboring atoms or ions.
- Lithium has a higher polarizability compared to other elements in its group.
- The higher polarizability of lithium allows it to distort the electron cloud of neighboring atoms, promoting the formation of covalent bonds by sharing electrons.

5. Metallic Character:
- Lithium exhibits more metallic character compared to other elements in its group.
- The metallic character of an element decreases as we move down a group.
- The more metallic character of lithium makes it more likely to form covalent compounds as it has a greater tendency to share electrons rather than losing them to form ionic compounds.

In conclusion, the greater tendency of lithium to form covalent compounds compared to other elements in its group can be attributed to its smaller atomic and ionic radii, lower electronegativity and ionization energy, higher polarizability, and greater metallic character. These factors make lithium more willing to share electrons in covalent bonds rather than forming ionic compounds.