Draw the Lewis structures for $\mathrm{SeO}_{2}, \mathrm{PCl}_{3}, \mathrm{NNO}, \mathrm{COS},\( and \)\mathrm{PF}_{3} .$ Which of the compounds are polar? Which of the compounds exhibit at least one bond angle that is approximately \(120^{\circ}\) Which of the compounds exhibit \(s p^{3}\) hybridization by the central atom? Which of the compounds have a linear molecular structure?

Using the element's group number, determine the number of valence electrons and draw the Lewis structures for each. Remember to satisfy the octet rule whenever possible. 1. SeO₂: Selenium (Se) is in Group 16 and so has 6 valence electrons. Oxygen (O) is also in Group 16 and has 6 valence electrons. Draw a Lewis structure where Selenium is the central atom, connected to two Oxygen atoms, with double bonds and lone electron pairs completing the octet for each atom: O = Se = O Se: 6 valence electrons 2 Oxygens: 2 x 6 valence electrons = 12 valence electrons Total valence electrons = 18 2. PCl₃: Phosphorus (P) is in Group 15 with 5 valence electrons. Chlorine (Cl) is in Group 17 with 7 valence electrons. Draw a Lewis structure where Phosphorus is the central atom, connected to three Chlorine atoms, each by single bonds and lone electron pairs completing the octet for each atom: Cl - P - Cl | Cl P: 5 valence electrons 3 Chlorines: 3 x 7 valence electrons = 21 valence electrons Total valence electrons = 26 3. NNO: There are two possible structures for NNO, i.e., N-N=O or N=N=O. The second structure N=N=O is a correct representation after verifying the formal charges: N = N = O Each Nitrogen: 5 valence electrons Oxygen: 6 valence electrons Total valence electrons = 16 4. COS: Carbon (C) is in Group 14 with 4 valence electrons. Oxygen (O) and Sulfur (S) are in Group 16 with 6 valence electrons each. Draw a Lewis structure where Carbon is the central atom, connected to Oxygen by a double bond, connected to Sulfur by a double bond, and lone electron pairs completing the octet for Oxygen and Sulfur: O = C = S C: 4 valence electrons O and S: 2 x 6 valence electrons = 12 valence electrons Total valence electrons = 16 5. PF₃: Phosphorus (P) is in Group 15 with 5 valence electrons. Fluorine (F) is in Group 17 with 7 valence electrons. Draw a Lewis structure with Phosphorus as the central atom, connected to three Fluorine atoms, each by single bonds, and lone electron pairs completing the octet for each atom: F - P - F | F P: 5 valence electrons 3 Fluorines: 3 x 7 valence electrons = 21 valence electrons Total valence electrons = 26

Determine the polarity of each compound by checking if the molecule is symmetrical or has a net dipole moment due to differences in electronegativity between the atoms: 1. SeO₂: Polar, due to the bent structure and difference in electronegativity between Se and O atoms. 2. PCl₃: Polar, due to the trigonal pyramid structure and difference in electronegativity between P and Cl atoms. 3. NNO: Polar, due to the bent structure and difference in electronegativity between N and O atoms. 4. COS: Polar, due to the linear structure and difference in electronegativity between C, O, and S atoms. 5. PF₃: Polar, due to the trigonal pyramid structure and difference in electronegativity between P and F atoms.

Based on their Lewis structures, the following compounds have a bond angle of approximately 120°: - SeO₂: The bond angle is approximately 120° due to its bent structure. - COS: The bond angle is 180°, so it does not meet the 120° criterion.

Look at the molecular geometry of the central atom in each compound to determine if sp³ hybridization is present: - PCl₃: The central Phosphorus atom is sp³ hybridized, with a tetrahedral molecular geometry. - PF₃: The central Phosphorus atom is sp³ hybridized, with a tetrahedral molecular geometry.

Based on the Lewis structures, the compounds with linear molecular structures are: - COS: The molecular geometry is linear with 180° bond angle. In summary, SeO₂, PCl₃, NNO, COS, and PF₃ are all polar compounds. SeO₂ has a bond angle of approximately 120°, while PCl₃ and PF₃ have sp³ hybridization by the central atom. COS has a linear molecular structure.