Question 1

Which of the following statements best describes the octet rule as it applies to Lewis structures?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their valence shell.

Question 2

When drawing the Lewis structure for $$CO_2$$, how many total valence electrons must be accounted for?

Accepted Answer

$$16$$

Question 3

Which of the following is the correct Lewis structure for $$CO_2$$?

Accepted Answer

O=C=O, with each O atom having 4 lone electrons

Question 4

What is the correct sequence of steps for drawing a Lewis structure, according to the provided rules?

Accepted Answer

Count valence electrons, draw skeleton, fill octets, place extra electrons, check octet rule

Question 5

How many lone pairs are present on the central atom in $$PCl_3$$?

Accepted Answer

$$1$$

Question 6

Which molecule below exhibits resonance structures?

Accepted Answer

$$CO_3$$^{2-}$$

Question 7

What does a resonance structure indicate about a molecule?

Accepted Answer

There are multiple valid Lewis structures due to the location of double or triple bonds.

Question 8

In the Lewis structure for $$CO_3$$^{2-}$$, how many total valence electrons are present?

Accepted Answer

$$24$$

Question 9

Which of the following best explains why hydrogen only forms one bond in Lewis structures?

Accepted Answer

Hydrogen only needs 2 electrons to fill its valence shell.

Question 10

A student draws the Lewis structure for $$CH_2O as $$shown below. What is incorrect about this structure?

$$H - C - O - H ($$all single bonds, no lone pairs shown)

Accepted Answer

The central carbon does not have a double bond to oxygen, so the octet rule is not satisfied.

Question 11

Which of the following is a correct step when drawing the Lewis structure for a polyatomic ion with a negative charge?

Accepted Answer

Add electrons equal to the magnitude of the negative charge to the total valence electron count.

Question 12

Which of the following molecules would you expect to have a central atom with an incomplete octet?

Accepted Answer

$$BH_3$$

Question 13

If a molecule has more electrons than needed to fill all atoms' octets, what should you do with the extra electrons?

Accepted Answer

Place them as lone pairs on the central atom.

Question 14

Which of the following best describes a covalent bond in a Lewis structure?

Accepted Answer

A shared pair of electrons between two atoms.

Question 15

How many resonance structures can be drawn for $$CO_3$$^{2-}$$?

Accepted Answer

$$3$$

Question 16

Which of the following is a correct Lewis structure for $$PCl_3$$?

Accepted Answer

A central P atom with three single bonds to Cl atoms and one lone pair on P.

Question 17

Which of the following is the correct Lewis structure for methane ($$CH_4$$)?

Accepted Answer

A central C atom with four single bonds to four H atoms.

Question 18

Which of the following best explains why resonance structures are important in chemistry?

Accepted Answer

They show that the actual structure is a hybrid of multiple possible structures, affecting properties like bond length.

Question 19

A student is asked to draw the Lewis structure for $$CO_3$$^{2-}$$. After drawing three resonance structures, what should the student do next to check their work?

Accepted Answer

Verify that all atoms (except H) have 8 electrons and the total number of electrons matches the calculated total.

Lewis Structures: Drawing and Interpreting Covalent Compounds

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