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Read the following statements. Which ones are correct? Be sure to explain how you know. BF3 and PFs are examples of exceptions to the octet rule. II. BF,¯ and BFg-NH3 are examples of violations of the octet rule. III. Expanded valence shells occur most often when the central atom is bonded to a small, electronegative element. IV. The central atoms most capable of having expanded valence shells come from rows 3, 4, and 5 of the periodic table.

1. How can you tell if a compound is covalent? 2. What distinguishes a covalent bond from an ionic bond? 3. How do you know how many valence electrons an atom has? 4. What is electronegativity? Is electronegativity a property of atoms or bonds? 5. What is polarity? Is polarity a property of atoms or bonds? 6. Describe in detail the N-F bond in terms of the relevant electronegativities and polarities. 7. What does VSEPR stand for and how does it allow one to predict the shapes of covalent molecules?

Write Lewis structures that obey the octet rule for each of the following. a. HCN b. PH3 c. CHCl3 d. NH4+ e. H2CO f. SeF2 g. CO2 h. O2 i. HBr Except for HCN and H2CO, the first atom listed is the central atom. For HCN and H2CO , carbon is the central atom.

Read the following statements. Which ones are correct? Be sure to explain how you know. I. BF3 and PF5 are examples of exceptions to the octet rule. II. BF4¯ and BF3-NH3 are examples of violations of the octet rule. III. Expanded valence shells occur most often when the central atom is bonded to a small, electronegative element. IV. The central atoms most capable of having expanded valence shells come from rows 3, 4, and 5 of the periodic table.

Fill in the lone pairs on each atom to give every main group element except hydrogen an octet.

In each group of three bonds, which bond is likely to be the most polar? Which will be the least polar? а. С-Н, N-H, О-Н The most polar bond is and the least polar bond is b. О-Н, О-О, С-0 The most polar bond is and the least polar bond is c. Br-Br, Br-F, Br-O The most polar bond is and the least polar bond is d. N-F, N-I, N-Br The most polar bond is and the least polar bond is

Which of the following is TRUE? 1. Resonance structures are real molecules that are in equilibrium with each other in solution. II. Resonance structures are drawings that differ in the position of electrons, not in the position of atoms. III. The energy of the actual species is higher that the estimated energy of any of the species resonance structures. IV. Resonance structures are always equivalent. Select one: O A. IV OB. II O C. I D. III

Help please

Please draw the Lewis structure for each of the follow 1). HCN Of all the atoms in HCN, which is the most electronegative? (Where will the electrons spend most of their time?) a) 3). PC13 Most electronegative?