About 25 of the 92 natural elements are known to be essential to life. Which 4 of these 25
elements make up approximately 96% of living matter?
A) carbon, sodium, hydrogen, nitrogen
B) carbon, oxygen, phosphorus, hydrogen
C) oxygen, hydrogen, calcium, nitrogen
D) carbon, hydrogen, nitrogen, oxygen
E) carbon, oxygen, nitrogen, calcium

D

Trace elements are those required by an organism in only minute quantities. Which of the
following is a trace element that is required by humans and other vertebrates, but not by other
organisms such as bacteria or plants?
A) nitrogen
B) calcium
C) iodine
D) sodium
E) phosphorus

C

Which of the following statements is false?
A) Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter.
B) Some naturally occurring elements are toxic to organisms.
C) All organisms require the same elements in the same quantities.
D) Iron is an example of an element needed by all organisms.
E) Approximately one-quarter of the natural elements are essential elements.

C

Why is each element unique and different from other elements with respect to its chemical
properties?
A) Each element has a unique atomic mass.
B) Each element has a unique atomic number.
C) Each element has a unique number of protons.
D) Each element has a unique number of neutrons.
E) Each element has different radioactive properties.

C

Knowing just the atomic mass of an element allows inferences about which of the following?
A) the number of electrons in the element
B) the number of protons in the element
C) the number of neutrons in the element
D) the number of protons plus neutrons in the element
E) the number of protons plus electrons in the element

D

In what way are elements in the same column of the periodic table the same?
A) They have the same number of protons.
B) They have the same number of neutrons.
C) They have the same number of electrons.
D) They have the same number of electrons in their valence shell.
E) They have the same number of electron shells.

D

The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a
correct statement concerning nitrogen?
A) The nitrogen atom has a mass number of approximately 7 and an atomic number of 14.
B) The nitrogen atom has a mass number of approximately 14 and an atomic number of 7.
C) The nitrogen atom has a mass number of approximately 14 and an atomic number of 14.
D) The nitrogen atom has a mass number of approximately 7 and an atomic number of 21.
E) The nitrogen atom has a mass number of approximately 14 and an atomic number of 21

B

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers
of 92, 94, 95, 96, 97, 98, and 100. Therefore, which of the following can be true?
A) Molybdenum atoms can have between 50 and 58 neutrons.
B) The isotopes of molybdenum have different electron configurations.
C) The isotopes of molybdenum can have between 50 and 58 protons.
D) The isotopes of molybdenum have between 50 and 58 neutrons and have different electron
configurations.
E) The isotopes of molybdenum have between 50 and 58 protons and have different electron
configurations.

A

Carbon-12 is the most common isotope of carbon and has a mass number of 12. However, the
atomic mass of carbon is slightly more than 12 daltons. Why?
A) The atomic mass does not include the mass of electrons.
B) Some carbon atoms in nature have an extra proton.
C) Some carbon atoms in nature have more neutrons.
D) Some carbon atoms in nature have a different valence electron distribution.
E) Some carbon atoms in nature have undergone radioactive decay.

C

One difference between carbon-12 (C) and carbon-14 (C) is that carbon-14 has
A) two more protons than carbon-12.
B) two more electrons than carbon-12.
C) two more neutrons than carbon-12.
D) two more protons and two more neutrons than carbon-12.
E) two more electrons and two more neutrons than carbon-12.

C

An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?
A) 0
B) 2
C) 4
D) 6
E) 2 or 4

B

The atomic number of nitrogen is 7. Nitrogen-15 is heavier than nitrogen-14 because the
atomic nucleus of nitrogen-15 contains how many neutrons?
A) 6
B) 7
C) 8
D) 12
E) 14

C

Electrons exist only at fixed levels of potential energy. However, if an atom absorbs
sufficient energy, a possible result is that
A) an electron may move to an electron shell farther away from the nucleus.
B) an electron may move to an electron shell closer to the nucleus.
C) the atom may become a radioactive isotope.
D) the atom would become a positively charged ion, or cation, and become a radioactive isotope.
E) the atom would become a negatively charged ion, or anion.

A

The atomic number of neon is 10. Therefore, which of the following is most correct about an
atom of neon?
A) It has 8 electrons in its outer electron shell.
B) It is inert.
C) It has an atomic mass of 10 daltons.
D) It has 8 electrons in its outer electron shell and it is inert.
E) It has 8 electrons in its outer electron shell, it is inert, and it has an atomic mass of 10 daltons.

D

From its atomic number of 15, it is possible to predict that the phosphorus atom has
A) 15 neutrons.
B) 15 protons.
C) 15 electrons.
D) 8 electrons in its outermost electron shell.
E) 15 protons and 15 electrons.

E

The atomic number of each atom is given to the left of each of the following elements.
Which of the atoms has the same valence as carbon (C)?
A) 7N nitrogen
B) 9F fluorine
C) 10Ne neon
D) 12Mg magnesium
E) 14Si silicon

E

Two atoms appear to have the same mass number. These atoms
A) must have the same atomic number.
B) must have the same number of electrons.
C) must have the same chemical properties.
D) must have the same number of protons + neutrons.
E) must have the same atomic number, the same number of protons + neutrons, the same number
of electrons, and the same chemical properties.

D

Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a
form of radioactive decay whereby a neutron turns into a proton, which is retained in the nucleus,
and emits radiation in the form of an electron. What is the product of such radioactive decay of
phosphorus-32?
A) phosphorus-31
B) a positively charged phosphorus-31 ion
C) a negatively charged phosphorus-32 ion
D) sulfur-32 (atomic number 16)
E) the conversion of the phosphorus-32 atom into pure energy

D

Fluorine has an atomic number of 9 and a mass number of 19. How many electrons are
needed to complete the valence shell of a fluorine atom?
A) 1
B) 3
C) 0
D) 7
E) 9

A

Oxygen has an atomic number of 8 and a mass number of 16. Thus, what is the atomic mass
of an oxygen atom?
A) approximately 8 grams
B) approximately 8 daltons
C) approximately 16 grams
D) approximately 16 daltons
E) approximately 24 grams

D

What is the maximum number of electrons in a single 2 p orbital of an atom?
A) 1
B) 2
C) 3
D) 4
E) 5

B

An atom with atomic number 12 would have what type of chemical behavior in bonding with
other elements?
A) It would form ions with a +1 charge.
B) It would form ions with a +2 charge.
C) It would form ions with a -1 charge.
D) It would form ions with a -2 charge.
E) It would form two covalent bonds with other atoms.

B

A covalent chemical bond is one in which
A) electrons are removed from one atom and transferred to another atom so that the two atoms
become oppositely charged.
B) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms.
C) outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron
shells of both atoms.
D) outer-shell electrons of one atom are transferred to fill the inner electron shell of another
atom.
E) an electron occupies a hybrid orbital located between the nuclei of two atoms.

C

If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen
(atomic number 1), which of the following molecules would be formed?
A) S–H
B) H–S–H
C)

D)

E) H = S = H

B

What is the maximum number of covalent bonds an element with atomic number 8 can make
with hydrogen?
A) 1
B) 2
C) 3
D) 4
E) 6

B

Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following
statements is correct about the atoms in ammonia (NH3)?
A) Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative
charge.
B) The nitrogen atom has a full positive charge; each hydrogen atom has a full positive charge.
C) Each hydrogen atom has a partial negative charge; the nitrogen atom has a full positive
charge.
D) The nitrogen atom has a partial positive charge; each hydrogen atom has a partial negative
charge.
E) There are covalent bonds between the hydrogen atoms and polar bonds between each
hydrogen atom and the nitrogen atom.

A

When two atoms are equally electronegative, they will interact to form
A) hydrogen bonds.
B) van der Waals interactions.
C) polar covalent bonds.
D) nonpolar covalent bonds.
E) ionic bonds.

D

What results from an unequal sharing of electrons between atoms?
A) a nonpolar covalent bond
B) a polar covalent bond
C) an ionic bond
D) radioactive decay
E) a hydrophobic interaction

B

A covalent bond is likely to be polar when
A) one of the atoms sharing electrons is much more electronegative than the other atom.
B) the two atoms sharing electrons are equally electronegative.
C) oxygen is one of the two atoms sharing electrons.
D) one of the atoms has absorbed more energy than the other atom.
E) the two atoms sharing electrons are different elements.

A

Which of the following molecules contains the most polar covalent bond?

D

In comparing covalent bonds and ionic bonds, which of the following would you expect?
A) An atom can form covalent bonds with multiple partner atoms, but only a single ionic bond
with a single partner atom.
B) Covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly
equal to completely unequal sharing of electrons.
C) Both involve electrical attraction between the electrons of one atom and the nucleus of the
other atom.
D) Ionic interactions remain when covalent bonds are broken in water. Ionic bonds are much
stronger than covalent bonds.

B

What is the difference between covalent bonds and ionic bonds?
A) Covalent bonds are formed between atoms to form molecules; ionic bonds are formed
between atoms to form compounds.
B) Covalent bonds involve the sharing of pairs of electrons between atoms; ionic bonds involve
the sharing of single electrons between atoms.
C) Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the
electrical attraction between atoms.
D) Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the
sharing of protons between atoms.
E) Covalent bonds involve the transfer of electrons between atoms; ionic bonds involve the
sharing of electrons between atoms.

C

In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, Cl. What is the cation
of NH4Cl?
A) N, with a charge of +1
B) NH, with a charge of +1
C) H3, with a charge of +1
D) NH4, with a charge of +1
E) NH4, with a charge of +4

D

The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the
formula for magnesium chloride?
A) MgCl
B) MgCl2
C) Mg2Cl
D) Mg2Cl2
E) MgCl3

B

How many electron pairs are shared between carbon atoms in a molecule that has the
formula C2H4?
A) 0
B) 1
C) 2
D) 3
E) 4

C

Which bond or interaction would be difficult to disrupt when compounds are put into water?
A) covalent bond
B) hydrogen bond
C) van der Waals interaction
D) ionic bond
E) either covalent bond or ionic bond

A

Van der Waals interactions result when
A) hybrid orbitals overlap.
B) electrons are not symmetrically distributed in a molecule.
C) molecules held by ionic bonds react with water.
D) two polar covalent bonds react.
E) a hydrogen atom loses an electron.

B

What bonding or interaction is most likely to occur among a broad array of molecules of
various types (polar, nonpolar, hydrophilic, hydrophobic)?
A) covalent bonding
B) polar covalent bonding
C) ionic bonding
D) hydrogen bonding
E) van der Waals interactions

E

Which of the following is (are) not considered to be a weak molecular interaction?
A) a covalent bond
B) a van der Waals interaction
C) an ionic bond in the presence of water
D) a hydrogen bond
E) both a hydrogen bond and a covalent bond

A

Which of the following would be regarded as compounds?
A) H2O, O2, and CH4
B) H2O and O2
C) O2 and CH4
D) CH4 and O2, but not H2O
E) H2O and CH4, but not O2

E

What is the maximum number of hydrogen atoms that can be covalently bonded in a
molecule containing two carbon atoms?
A) 2
B) 3
C) 4
D) 6
E) 8

D

Which of the following is true for this reaction?
3 H2 + N2 ↔ 2 NH3
A) The reaction is nonreversible.
B) Hydrogen and nitrogen are the reactants of the reverse reaction.
C) Hydrogen and nitrogen are the products of the forward reaction.
D) Ammonia is being formed and decomposed.
E) Hydrogen and nitrogen are being decomposed.

D

Forward and reverse reactions continue with no effect on the concentrations of the reactants
and products.
B) The concentrations of the products are higher than the concentrations of the reactants.
C) Forward and reverse reactions have stopped so that the concentration of the reactants equals
the concentration of the products.
D) Reactions stop only when all reactants have been converted to products.
E) There are equal concentrations of reactants and products, and the reactions have stopped.

A

Which of the following correctly describes any reaction that has reached chemical
equilibrium?
A) The concentration of the reactants equals the concentration of the products.
B) The rate of the forward reaction is equal to the rate of the reverse reaction.
C) All of the reactants have been converted to the products of the reaction.
D) All of the products have been converted to the reactants of the reaction.
E) Both the forward and the reverse reactions have stopped with no net effect on the
concentration of the reactants and the products.

B

Which of the following explains most specifically the attraction of water molecules to one
another?
A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) hydrophobic interaction

D

If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would
cause the most problems for this animal?
A) a surface coated with a thin film of water
B) a surface made with carbon and hydrogen atoms covalently bonded together
C) a surface made with carbon, hydrogen, and oxygen atoms covalently bonded together
D) a surface made with carbon, hydrogen, nitrogen, and oxygen atoms covalently bonded
together
E) a surface made with silicon and oxygen atoms covalently bonded together

B

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
A) hydrogen bonds.
B) nonpolar covalent bonds.
C) polar covalent bonds.
D) ionic bonds.
E) van der Waals interactions.

C

The slight negative charge at one end of one water molecule is attracted to the slight positive
charge of another water molecule. What is this attraction called?
A) a covalent bond
B) a hydrogen bond
C) an ionic bond
D) a hydrophilic bond
E) a van der Waals interaction

B