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For a tetrahedral molecule such as difluoromethane with two types of atom bonded to the central atom, the C-F bond to the more electronegative substituent (F) will involve a carbon orbital with less s character than the C-H bond, so that the angle between the C-F bonds is less than the tetrahedral bond angle of 109.5°.
For this molecule, carbon sp 2 hybridises, because one π (pi) bond is required for the double bond between the carbons and only three σ bonds are formed per carbon atom. In sp 2 hybridisation the 2s orbital is mixed with only two of the three available 2p orbitals, usually denoted 2p x and 2p y. The third 2p orbital (2p z) remains unhybridised.
The electronegativity of an atom changes depending on the hybridization of the orbital employed in bonding. Electrons in s orbitals are held more tightly than electrons in p orbitals. Hence, a bond to an atom that employs an sp x hybrid orbital for bonding will be more heavily polarized to that atom when the hybrid orbital has more s character.
Electronegativity is not a uniquely defined property and may depend on the definition. The suggested values are all taken from WebElements as a consistent set. Many of the highly radioactive elements have values that must be predictions or extrapolations, but are unfortunately not marked as such.
[6] [7] For example, in CH 4, the four electrons from the 1s orbitals of the hydrogen atoms and the valence electrons from the carbon atom (2 in s and 2 in p) occupy the bonding molecular orbitals, σ and π. [6] The delocalized MOs of the carbon atom in the molecule of methane can then be localized to give four sp 3 hybrid orbitals.
The type of bonding can be explained in terms of orbital hybridisation. In ethylene each carbon atom has three sp 2 orbitals and one p-orbital. The three sp 2 orbitals lie in a plane with ~120° angles. The p-orbital is perpendicular to this plane. When the carbon atoms approach each other, two of the sp 2 orbitals overlap to form a sigma bond.
In terms of frontier molecular orbital theory, the Lowest Unoccupied Molecular Orbital (LUMO) of the oxocarbenium ion is a π* orbital that has the large lobe on the carbon atom; the more electronegative oxygen contributes less to the LUMO. Consequently, in an event of a nucleophilic attack, the carbon is the electrophilic site.
Carbon and each oxygen atom will have a 2s atomic orbital and a 2p atomic orbital, where the p orbital is divided into p x, p y, and p z. With these derived atomic orbitals, symmetry labels are deduced with respect to rotation about the principal axis which generates a phase change, pi bond ( π ) [ 26 ] or generates no phase change, known as a ...