Question 1

Which of the following molecules or ions violates the octet rule by having fewer than eight electrons around the central atom?

Accepted Answer

$$ \mathrm{$$BCl_3$$} $$

Question 2

What is the electron domain geometry (EDG) and molecular geometry (MG) of $$ \mathrm{SF_4$} $$?

Accepted Answer

EDG: trigonal bipyramidal, MG: seesaw

Question 3

Which of the following best explains why $$ \mathrm{$$PBr_6$$^{2-}} $$ can have more than eight electrons around phosphorus?

Accepted Answer

Phosphorus is in period 3 and can use d orbitals to expand its octet.

Question 4

Which of the following statements about resonance is correct?

Accepted Answer

Resonance involves the movement of electrons, not atoms.

Question 5

In the molecule $$ \mathrm{HNNH}  ($$with atoms bonded in this order), what is the hybridization of the nitrogen atoms to allow for the observed bonding and resonance?

Accepted Answer

sp

Question 6

Which of the following is the best Lewis structure for $$ \mathrm{NO^+} $$ based on formal charges?

Accepted Answer

$$ \mathrm{N \equiv O^+} $$

Question 7

What is the bond order of $$ \mathrm{NO}  as $$determined from its molecular orbital diagram?

Accepted Answer

$$ 2.5 $$

Question 8

Which of the following best describes the trend in repulsion strength according to VSEPR theory?

Accepted Answer

Lone pair-lone pair \u003e lone pair-bonding pair \u003e bonding pair-bonding pair

Question 9

Which of the following statements about the bond lengths in $$ \mathrm{C_2H_2} $$, $$ \mathrm{C_2H_4} $$, and $$ \mathrm{C_2H_6}  is $$correct?

Accepted Answer

Triple bonds are shorter than double bonds, which are shorter than single bonds.

Question 10

Which of the following is NOT a valid resonance structure for the acetate ion ($$ \mathrm{CH_3CO_2^-} $$)?

Accepted Answer

A structure where a hydrogen atom moves between oxygens.

Question 11

Which of the following best explains why the $$ \mathrm{Cl} $$ atom in chloromethane ($$ \mathrm{CH_3Cl} ) is $$considered mostly unhybridized?

Accepted Answer

Experimental evidence of electron density supports an unhybridized $$ \mathrm{Cl} .$$

Question 12

Which of the following is the strongest resonance contributor for the molecule $$ \mathrm{NCO^-} $$?

Accepted Answer

The structure with all octets satisfied and the negative charge on the most electronegative atom.

Question 13

Which of the following is true about the molecular orbital (MO) diagram for $$ \mathrm{NO^+} $$?

Accepted Answer

It has a bond order of 3.

Question 14

Which of the following statements about the $$ \mathrm{NO} $$ molecule is correct?

Accepted Answer

The best Lewis structure minimizes formal charges.

Question 15

Which of the following is a correct statement about the orbital overlap in $$ \mathrm{CH_3Cl} $$?

Accepted Answer

The C–Cl bond can be explained by overlap of C $$sp^3$$ and Cl p orbitals.

Question 16

Which of the following is NOT a criterion for identifying the best resonance structure?

Accepted Answer

Maximizing the number of atoms with formal charges.

Question 17

Which of the following molecules has a seesaw molecular geometry?

Accepted Answer

$$ \mathrm{SF_4$} $$

Question 18

Which of the following statements about the $$ \mathrm{NO^+} $$ ion is correct?

Accepted Answer

It is isoelectronic with $$ \mathrm{CO} .$$

Question 19

Which of the following is a correct statement about the bond angles in $$ \mathrm{SF_4$} $$?

Accepted Answer

The F–S–F bond angles are less than $$ 90^\circ $$ and less than $$ 120^\circ $$ due to lone pair repulsion.

Molecular Structure, Resonance, and Bonding in General Chemistry

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