Question 1

Which of the following best explains why water (H$_2$O) is considered a polar molecule?

Accepted Answer

The oxygen atom has a higher electronegativity than hydrogen, resulting in an unequal sharing of electrons and partial charges on the atoms.

Question 2

Which of the following statements about ionic bonds is correct?

Accepted Answer

Ionic bonds involve the complete transfer of one or more valence electrons from one atom to another.

Question 3

A neutral atom of carbon-14 ($^{14}_{6}C$) has how many neutrons?

Accepted Answer

$8$

Question 4

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between a hydrogen atom covalently bonded to F, O, or N and another electronegative atom.

Question 5

Which of the following molecules is an example of a nonpolar covalent bond?

Accepted Answer

$\mathrm{O_2}$

Question 6

Given the Lewis structure of water, which statement best explains why water molecules are attracted to each other?

Accepted Answer

The partial positive charge on hydrogen in one molecule is attracted to the partial negative charge on oxygen in another molecule.

Question 7

Which of the following best describes the difference in bond energy between ionic and covalent bonds in biological systems?

Accepted Answer

Covalent bonds have about 12 times the bond energy of ionic bonds under physiological conditions.

Question 8

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 9

Which of the following best explains why NaCl dissociates easily in water?

Accepted Answer

The polar water molecules surround and stabilize the Na$^+$ and Cl$^-$ ions, overcoming the ionic bond.

Question 10

Which of the following is the correct order of biological organization from smallest to largest?

Accepted Answer

Cell, tissue, organ, organism, population, community

Question 11

If an atom has 9 protons and a -1 charge, how many electrons does it have?

Accepted Answer

$10$

Question 12

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between two atoms, resulting in partial charges.

Question 13

Which of the following pairs of elements is most likely to form an ionic bond?

Accepted Answer

Na and Cl

Question 14

Which of the following best explains why ionic compounds have low bond energy in biological systems?

Accepted Answer

In water, the ions are surrounded by water molecules, which weakens the ionic bond and allows it to dissociate easily.

Question 15

Which of the following is a correct Lewis structure for methane ($\mathrm{CH_4}$)?

Accepted Answer

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

Question 16

Which of the following best describes the arrangement of electrons in the first energy shell of an atom?

Accepted Answer

It can hold a maximum of $2$ electrons, which fill as a pair.

Question 17

Which of the following is a correct example of a diatomic molecule?

Accepted Answer

$\mathrm{O_2}$

Question 18

Which of the following best explains why Maria lost points for her valence shell structure of oxygen?

Accepted Answer

She did not pair the electrons in the valence shell, which is required for a correct Lewis structure.

Question 19

Which of the following best describes the hydration shell that forms around a chloride ion (Cl$^-$) in water?

Accepted Answer

The partially positive hydrogen atoms of water molecules orient toward the chloride ion.

Atomic Structure, Chemical Bonds, and Water: Foundations for General Biology

Study Guide - Practice Questions