According to the vsepr model, a molecule with the general formula ab4 with two lone pairs on the central atom will have a molecular geometry.

According to the VSEPR model, a molecule with the general formula AB4 with two lone pairs on the central atom will have a tetrahedral molecular geometry. This geometry involves a central atom that is situated at the center of four other atoms which are found at the corner of a tetrahedron. It has a hybridization of sp3. When the four atoms in the corner are the same element, then the bond angles would measure 109.5 degrees. This geometry would lead to a non polar substance. Molecules which takes the shape of tetrahedral are known to be chiral. Examples are methane, ammonium ion, phosphate ion and carbon tetrachloride.

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Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.