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First, look at the position of the elements in the periodic table. Oxygen (O) is in group 16 and has 6 valence electrons, while Selenium (Se) is also in group 16 and has 6 valence electrons too. a. For \(\mathrm{SeO}_{3}\): - Total valence electrons = (Number of O atoms × Valence electrons in O) + (Number of Se atoms × Valence electrons in Se) = (3 × 6) + (1 × 6) = 24 b. For \(\mathrm{SeO}_{2}\): - Total valence electrons = (Number of O atoms × Valence electrons in O) + (Number of Se atoms × Valence electrons in Se) = (2 × 6) + (1 × 6) = 18

From the total number of valence electrons, we will distribute the electrons around the central atom (Se) for both molecules. a. \(\mathrm{SeO}_{3}\): 24 valence electrons - 1st oxygen bonded to Se: 2 electrons - 2nd oxygen bonded to Se: 2 electrons - 3rd oxygen bonded to Se: 2 electrons After connecting each oxygen atom to Se with a single bond, 18 electrons remain. Place these electrons as lone pairs on the oxygen atoms (each oxygen atom will get 3 lone pairs). The molecular geometry around the Se atom is determined by 3 bonding pairs (3 single bonds to O atoms) and 1 lone pair on the Se atom. According to VSEPR theory, this results in a trigonal pyramidal geometry with bond angles of approximately \(107.3^{\circ}\). b. \(\mathrm{SeO}_{2}\): 18 valence electrons - 1st oxygen bonded to Se: 2 electrons - 2nd oxygen bonded to Se: 2 electrons After connecting each oxygen atom to Se with a single bond, 14 electrons remain. Place these electrons as lone pairs on the oxygen atoms (each oxygen atom will get 3 lone pairs) and the remaining 2 electrons will form a lone pair on the Se atom. The molecular geometry around the Se atom is determined by 2 bonding pairs (2 single bonds to O atoms) and 2 lone pairs on the Se atom. According to VSEPR theory, this results in a bent or V-shaped geometry with bond angles of approximately \(104.5^{\circ}\). In conclusion, the molecular structures and bond angles for the given molecules are: a. \(\mathrm{SeO}_{3}\): Trigonal pyramidal, with bond angles of approximately \(107.3^{\circ}\) b. \(\mathrm{SeO}_{2}\): Bent or V-shaped, with bond angles of approximately \(104.5^{\circ}\)