Explain, why estrength of covalent bond in He2^2+ ,Li2^2+, Be2^2+ relative to their neutral molecules?
Answers
Explanation:
In MO theory, molecular orbitals form by the overlap of atomic orbitals. Atomic orbital energy correlates with electronegativity, as electronegative atoms hold electrons more tightly, lowering their energies. MO modeling is only valid when the atomic orbitals have comparable energy; when the energies differ greatly, the bonding mode becomes ionic. A second condition for overlapping atomic orbitals is that they have identical symmetry.
Two atomic orbitals can overlap in two ways, depending on their phase relationship. An orbital’s phase is a direct consequence of electrons’ wave-like properties. In graphical representations of orbitals, the orbital phase is depicted either by a plus or minus sign (with no relationship to electric charge) or by shading one lobe. The sign of the phase itself does not have physical meaning except when mixing orbitals to form molecular orbitals. Two same-sign orbitals have a constructive overlap, forming a molecular orbital with the bulk of the electron density located between the two nuclei. This MO is called the bonding orbital, and its energy is lower than that of the original atomic orbitals.