Question 1

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between two nonmetal atoms.

Question 2

Which molecule is an example of a compound that violates the octet rule by having less than an octet of electrons around the central atom?

Accepted Answer

$ \mathrm{BF_3} $

Question 3

Which of the following statements about the polarity of $ \mathrm{CO_2} $ is correct?

Accepted Answer

$ \mathrm{CO_2} $ is nonpolar because its linear geometry causes the bond dipoles to cancel.

Question 4

Which of the following molecules contains a triple covalent bond?

Accepted Answer

$ \mathrm{C_2H_2} $ (ethyne)

Question 5

A molecule of $ \mathrm{NH_3} $ (ammonia) is polar because:

Accepted Answer

It contains polar bonds and has an asymmetric (trigonal pyramidal) shape.

Question 6

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

Accepted Answer

It contains polar bonds and the bent shape causes the dipoles to add up.

Question 7

What is the correct Lewis structure for $ \mathrm{CH_4} $ (methane)?

Accepted Answer

A central carbon atom with four single bonds to four hydrogen atoms, and no lone pairs on carbon.

Question 8

Which of the following pairs of atoms will form a nonpolar covalent bond?

Accepted Answer

$ \mathrm{O} $ and $ \mathrm{O} $

Question 9

Which of the following molecules is nonpolar due to its molecular symmetry, despite having polar bonds?

Accepted Answer

$ \mathrm{BF_3} $

Question 10

A student is asked to draw the Lewis structure for $ \mathrm{SO_4^{2-}} $. What is the total number of valence electrons that must be accounted for?

Accepted Answer

32

Question 11

Which of the following best describes the difference between a single, double, and triple covalent bond?

Accepted Answer

A single bond shares one pair of electrons, a double bond shares two pairs, and a triple bond shares three pairs of electrons.

Question 12

Which of the following molecules is an example of a diatomic molecule with a triple bond?

Accepted Answer

$ \mathrm{N_2} $

Question 13

Which of the following statements about electronegativity and bond type is correct?

Accepted Answer

A bond with $ \Delta EN = 1.0 $ is likely polar covalent.

Question 14

Which of the following is a correct step in drawing the Lewis structure of a molecule?

Accepted Answer

Sum the valence electrons of all atoms in the molecule.

Question 15

Which of the following molecules is expected to be polar?

Accepted Answer

$ \mathrm{CH_3Br} $

Question 16

A molecule has polar bonds but is nonpolar overall. Which of the following best explains this observation?

Accepted Answer

The molecule has a symmetrical geometry causing the bond dipoles to cancel.

Question 17

Which of the following is an exception to the octet rule due to having more than eight electrons around the central atom?

Accepted Answer

$ \mathrm{PF_5} $

Question 18

Which of the following best describes the relationship between molecular symmetry and polarity?

Accepted Answer

Molecules with polar bonds and symmetrical charge distribution are nonpolar.

Question 19

Which of the following real-world substances is a molecular compound formed by covalent bonding?

Accepted Answer

Methane ($ \mathrm{CH_4} $)

Question 20

A chemist is analyzing a new compound and finds that it is composed of only nonmetals and has a low melting point. Which type of bonding is most likely present in this compound?

Accepted Answer

Covalent bonding

Covalent Bonds: Formation, Types, Lewis Structures, Electronegativity, and Polarity

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