(N/A) The Lewis covalent bond theory,while useful for understanding the formation of covalent bonds,has several limitations:
$1$. It does not explain the shape and geometry of molecules.
$2$. It fails to explain the stability of molecules with an odd number of electrons (e.g.,$NO$,$NO_2$).
$3$. It cannot explain the stability of molecules where the central atom has an incomplete octet (e.g.,$BeCl_2$,$BF_3$) or an expanded octet (e.g.,$PF_5$,$SF_6$).
$4$. It does not provide any information regarding the energy of the molecule or the relative stability of different structures.
$5$. It does not account for the magnetic properties of molecules,such as the paramagnetic nature of $O_2$.