How BeF2 exists as by doing so Be will have only 4 electrons in its valence shell
well done! Shubham keep contributing .....i have just modified your answer.
Be has sp hybrid Orbitals has 2 electrons in its outermost shell.BeF2 form covalent bond with F atoms with sp hybridization but each of F atom has 3 lone pairs and Be has empty 2p orbital shell to accomadate such 4 electron (two from each fluorine atom).This result in back bonding between fluorine and beryllium atom.