Question 1

Which statement best describes a covalent bond?

Accepted Answer

A bond in which two atoms share one or more pairs of electrons.

Question 2

According to the Lewis structure rules, what is the first step in drawing the Lewis structure for a molecule?

Accepted Answer

Count the total number of valence electrons for all atoms.

Question 3

Which of the following molecules is an example of an exception to the octet rule due to an incomplete octet?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 4

What is the formal charge on the central carbon atom in the Lewis structure of $$\mathrm{CO_2$}$$?

Accepted Answer

$$0$$

Question 5

Which of the following best explains why $$\mathrm{H_2O} is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, and the bent geometry creates a net dipole.

Question 6

Which of the following molecules contains a triple covalent bond?

Accepted Answer

$$\mathrm{N_2$}$$

Question 7

What is the correct Lewis structure for the nitrate ion $$\mathrm{NO_3$^-}$$?

Accepted Answer

A structure with one double bond and two single bonds to oxygen, with resonance among the oxygens.

Question 8

Which element has the highest electronegativity according to the periodic trend?

Accepted Answer

Fluorine ($$\mathrm{F})$$

Question 9

In the molecule $$\mathrm{CO_2$}$$, what is the oxidation state of carbon?

Accepted Answer

$$+4$$

Question 10

Which of the following is a correct statement about resonance structures?

Accepted Answer

Resonance structures are used to represent delocalized electrons within a molecule.

Question 11

Which molecule is an example of an expanded octet?

Accepted Answer

$$\mathrm{SF_6$}$$

Question 12

What is the formal charge on the oxygen atom in $$\mathrm{CO}$$ where oxygen has three lone pairs and is single bonded to carbon?

Accepted Answer

$$-1$$

Question 13

Which of the following is true about the Lewis dot symbol for chlorine ($$\mathrm{Cl}$$)?

Accepted Answer

It has 7 dots around the symbol.

Question 14

Which molecule is an example of a molecule with an odd number of electrons (a free radical)?

Accepted Answer

$$\mathrm{NO}$$

Question 15

Which of the following best describes the concept of electronegativity?

Accepted Answer

The ability of an atom to attract electrons in a chemical bond.

Question 16

Which of the following molecules has a nonpolar covalent bond?

Accepted Answer

$$\mathrm{H_2$}$$

Question 17

What is the total number of valence electrons in the Lewis structure of $$\mathrm{CO_3$^{2-}}$$?

Accepted Answer

$$24$$

Question 18

Which of the following is a correct application of the octet rule?

Accepted Answer

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

Question 19

Which of the following is true about formal charge in Lewis structures?

Accepted Answer

Formal charge is calculated as the number of valence electrons minus the number of lone pair electrons minus half the number of bonding electrons.

Question 20

Which of the following molecules is most likely to exhibit resonance?

Accepted Answer

$$\mathrm{O_3$}$$

La liaison chimique I : la liaison covalente et les structures de Lewis

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