a) Lewis Structure:
The Lewis structure for selenium tetrafluoride (SeF4) can be drawn by placing the selenium atom in the center with four fluorine atoms surrounding it. Selenium has six valence electrons, and each fluorine has seven. In the Lewis structure, selenium forms single bonds with each of the four fluorine atoms, using up four of its valence electrons. This leaves two lone pairs of electrons on the selenium atom. The structure would look like this:
F | F—Se—F | F
b) Hybridization of Se:
The hybridization of selenium in SeF4 is sp3d. This indicates that one s orbital, three p orbitals, and one d orbital are hybridized to form five equivalent hybrid orbitals, which are used to form bonds and hold lone pairs.
c) Electron Geometry:
The electron geometry of SeF4 is trigonal bipyramidal. This geometry arises from the arrangement of the five electron pairs (four bonding pairs and one lone pair) around the central selenium atom.
d) Molecular Geometry:
The molecular geometry of SeF4 is seesaw. This is due to the presence of one lone pair on the selenium atom, which causes the arrangement of the bonding pairs to adjust from a symmetrical trigonal bipyramidal shape to a seesaw shape.
e) Expected Degree Angles:
The bond angles in SeF4 vary due to its seesaw molecular geometry. The expected angles are approximately 120 degrees between the equatorial fluorine atoms and around 90 degrees between the axial and equatorial fluorine atoms. However, the exact angles can be slightly different due to the influence of the lone pair on the electron geometry.