1. (17 points) Based on the descriptions of the following molecular compounds (i) draw the best Lewis
structure, (ii) provide the central atom hybridization, and (iii) determine the molecular
geometry. In each case, the central atom is a main group element capable of forming polar-
covalent bonds with its bonding atoms.
(a) The unknown element, X, reacts with fluorine to produce XF4. The molecule experiences both
London-dispersion forces and dipole-dipole interactions in the condensed phase.
(b) The unknown element, Y, reacts with hydrogen to produce YH3. The gas-phase molecule does
not possess a permanent dipole moment.
(c) The unknown element, Z, reacts with fluorine and hydrogen to produce two products with the
chemical formula, ZF2H2. One product only experiences London-dispersion forces in the
condensed phase, the second experiences both London-dispersion forces and dipole-dipole
interactions in the condensed phase, and both products share the same electron domain
geometry. Draw and analyze both products!