Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Explain how resonance affects the bond lengths in the carbonate ion ($CO_3^{2-}$). State the setup, compute carefully, and interpret the result.

Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Use VSEPR theory to predict the molecular geometry of sulfur tetrafluoride ($SF_4$). Provide a concise written explanation.

Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Determine which bond is more polar: C-F or C-O. Justify using electronegativity trends. State the setup, compute carefully, and interpret the result.

Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Compare the properties of NaCl and diamond to distinguish between ionic and covalent network solids. Provide a concise written explanation.

Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Draw the Lewis structure for the nitrate ion ($NO_3^-$) and specify the number of lone pairs on the central atom. State the setup, compute carefully, and interpret the result.

Advanced timed challenge: In a molecular and ionic structure setting, use Lewis structures, formal charge, resonance, VSEPR geometry, bond polarity, and ionic versus covalent bonding. Calculate the formal charge of the central oxygen atom in ozone ($O_3$). Provide a concise written explanation.