Chapter 2 Mastering

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Therefore, which of the following can be true? Isotopes of molybdenum have different numbers of electrons. Molybdenum atoms can have between 50 and 58 neutrons. Molybdenum atoms can have between 50 and 58 protons. Molybdenum atoms can have between 50 and 58 electrons.

Molybdenum atoms can have between 50 and 58 neutrons.

Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons? Protons at the atom's surface determine the atom's behavior. 99% of the atom's mass consists of protons. The proton's negative charge holds electrons in the atom. The nucleus doesn't change in stable isotopes. None of these. Elements are defined by the number of protons.

None of these. Elements are defined by the number of protons. Protons give an enduring basis for atomic behavior because they are permanently anchored in the nucleus, where their attraction determines how many electrons the atom can hold. By contrast, electrons come and go, and the numbers vary.

Which of these relationships is true of an uncharged atom? The atomic mass is equal to the atomic number. The number of protons is equal to the number of electrons. The number of electrons is equal to the number of neutrons. The atomic mass is equal to the number of electrons. The number of neutrons is equal to the number of protons.

The number of protons is equal to the number of electrons.

Which statement is true of the energy levels of electrons in shells? Electrons must lose energy to move from the first to the second shell. All the electrons in an atom have similar amounts of energy. The valence shell has higher energy than other occupied shells. All of the above. None of the above.

The valence shell has higher energy than other occupied shells.

Which of these refers to atoms with the same atomic number but different atomic masses? These atoms have different numbers of protons. These atoms have different numbers of electrons. These atoms are isomers. These atoms are different elements. These atoms are isotopes.

These atoms are isotopes. Atoms with the same atomic number and different atomic masses are referred to as isotopes.

Magnesium has an atomic number of 12. What is the most stable charge for a magnesium ion? a -2 charge a -1 charge a +1 charge a +2 charge

a +2 charge

water

hydro-

In salt, what is the nature of the bond between sodium and chlorine? hydrophobic polar covalent nonpolar covalent ionic hydrogen

ionic

A carbon atom and a hydrogen atom form what type of bond in a molecule? nonpolar covalent bond hydrogen bond Van der Waals interaction polar covalent bond ionic bond

nonpolar covalent bond Atoms with similar electronegativities form nonpolar covalent bonds.

first

prim-

What type of bond joins the carbon atom to each of the hydrogen atoms? double (nonpolar) covalent polar covalent ionic hydrogen single (nonpolar) covalen

single (nonpolar) covalent Each carbon-hydrogen bond involves a single pair of equally shared electrons.

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ... the first shell must fill before the second shell can have electrons. no shell can hold more than 2 electrons. the first shell shouldn't have 3 electrons. the second shell should have 8 electrons. the second shell can't have 4 electrons.

the first shell shouldn't have 3 electrons.

What determines the types of chemical reactions that an atom participates in? its atomic mass the number of electrons in the outermost electron shell its atomic number the number of electrons in the innermost electron shell the number of protons it contains

the number of electrons in the outermost electron shell

Knowing the atomic mass of an element allows inferences about which of the following? the number of protons plus neutrons in the element the number of protons plus electrons in the element the number of electrons in the element the number of protons in the element

the number of protons plus neutrons in the element

Two atoms always represent the same element if they have ... the same number of electrons. the same number of protons. the same number of particles in the nucleus. the same number of shells. the same mass number.

the same number of protons. The number of protons defines a chemical element. The number of neutrons and electrons can differ among atoms of the same element.

two

di-

three

tri-

How many neutrons are present in the nucleus of a phosphorus-32 (32P) atom (see the figure above)? 15 16 17 32

17

loosening, split apart

-lysis

An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have? 0 5 11 16 6

5 The atomic number is equal to the number of protons.

Choose the appropriate balanced equation for the following chemical reaction. C6H6 + H2 → C6H12 C6H6 + 6 H2 → C6H12 C6H6 + 6 H2 → 2 C6H12 2 C6H6 + 6 H2 → 2 C6H12 C6H6 + 3 H2 → C6H12 None of the above.

C6H6 + 3 H2 → C6H12

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________. C; it has 6 electrons. C; it has 6 protons. N; it has 6 electrons. N; it has 6 protons. O; its mass number is 12.

C; it has 6 protons. Atoms represent the element carbon (C) if they have six protons.

against

anti-

to fear

-phob

What is the molecular mass of caffeine (C8H10N4O2)? 43.0 138.2 178.2 194.2 None of the above.

194.2 Correct! This is the correct molecular mass of caffeine.

How many grams of glucose would you need to make 1 liter of an aqueous 0.5M glucose solution? (Atomic masses: C = 12.01, H = 1.008, O = 16.00.) 90.08 grams of glucose 180.2 grams of glucose 60.05 grams of glucose 70.36 grams of glucose 120.1 grams of glucose

90.08 grams of glucose

What type of bond is joining the two hydrogen atoms?

covalent A covalent bond is one in which electron pairs are shared.

A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____. compound isotope molecule proton element

element

equal

iso-

single

mono-

first

proto-

Sort the subatomic particles according to their masses.

The proton and neutron both have masses of about 1 amu, whereas the electron mass is only about 5.5×10−4amu.

to

ad-

How many grams of water (H2O) are needed to react with 5.0 grams of ferric trichloride (FeCl3)? FeCl3 + 3 H2O → Fe(OH)3 + 3 HCl 0.18 g H2O 1.7 g H2O 0.55 g H2O 0.99 g H2O None of the above.

1.7 g H2O It would take 1.7 g of H2O to react with 5.0 grams of FeCl3

Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have? 28 81 9 19 10

10 Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ... 9 protons. 7 electrons. mass number 16, atomic number 7. 10 neutrons. All of the above.

10 neutrons. Isotopes have the same number of protons; different numbers of neutrons.

The innermost electron shell of an atom can hold up to _____ electrons. 2 18 1 32 8

2

Choose the correct balanced equation for the following reaction. C8H18 + O2 → CO2 + H2O 4 C8H18 + 50 O2 → 32 CO2 + 36 H2O 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O C8H18 + 17 O2 → 8 CO2 + 18 H2O C8H18 + 12.5 O2 → 8 CO2 + 9 H2O None of the above

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

What is the mass number of an ion with 109 electrons, 159 neutrons, and a +1 charge?

269

This atom can form up to _____ single covalent bond(s). 4 3 1 0 2

4

Which statement is true of the atom shown in the diagram? An electron will move from the outer to the inner shell. The atom is in the excited state. The atom has more than one valence electron. All of the above. None of the above.

All of the above. The atom has a vacancy in its inner shell; an electron has moved to the outer (valence) shell. The result is an unstable excited state. An electron will move back to the inner shell, restoring the ground state as the atom gives off energy.

Which statement is true of atoms? Most of an atom's volume is filled with matter. Protons attract other protons. Protons repel electrons. Electrons determine the atom's size. All of the above.

Electrons determine the atom's size.

Which statement about the following reaction is true? 4 Fe + 3 O2 → 2 Fe2O3 Four grams of Fe reacts with 3 grams of O2 to form 2 grams of Fe2O3. The reaction is not balanced. Four atoms of Fe react with 3 molecules of O2 to form 2 molecules of Fe2O3 Fe2O3 is the reactant in this reaction. None of the above

Four atoms of Fe react with 3 molecules of O2 to form 2 molecules of Fe2O3

Which of these figures correctly illustrates the nature of the bonding of H2O?

Oxygen is more electronegative than hydrogen.

Which model most accurately represents the current view of the structure of the atom? Probability model Planetary model

Probability model We cannot determine the exact motion of electrons. We can only compute the regions where electrons occur most of the time. To emphasize the uncertainty, a diagram showing random motion is more suitable than planetary paths.

Radioactive decay is likely to occur when ... protons break into neutrons and electrons. atoms collide with one another. an atom has too many neutrons. an electron hits the nucleus. an atom has too many electrons.

an atom has too many neutrons. The atomic nucleus becomes unstable if the ratio of protons to neutrons is too far from unity.

An ionic bond involves _____. the unequal sharing of an electron pair water avoidance the sharing of a single pair of electrons an attraction between ions of opposite charge no atoms other than sodium and chlorine

an attraction between ions of opposite charge

Atoms with the same number of protons but with different electrical charges _____. are different ions are different isotopes have different numbers of neutrons have different atomic masses have different atomic numbers

are different ions

About twenty-five of the ninety-two natural elements are known to be essential to life. Which four of these twenty-five elements make up approximately 96 percent of living matter? carbon, oxygen, phosphorus, hydrogen carbon, sodium, hydrogen, nitrogen oxygen, hydrogen, calcium, nitrogen carbon, hydrogen, nitrogen, oxygen

carbon, hydrogen, nitrogen, oxygen

A(n) _____ refers to two or more atoms held together by covalent bonds. molecule isotope community ion shell

molecule A molecule is defined as two or more atoms held together by covalent bonds.

of neither gender or type

neutr-

many

poly-

to love

-phil

with or together with

co-

What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons? 12 0 18 -1 6

6 This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.

The mass number of an atom is 15, and its atomic number is 7. The atom probably has... 7 electrons in the nucleus. 8 neutrons in the nucleus. at least 15 electrons. about as much mass in electrons as in protons. 7 units of negative charge in the nucleus.

8 neutrons in the nucleus.

What name is given to the bond between water molecules? hydrophobic ionic hydrogen polar covalent single (nonpolar) covalent

A hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.

Given what you know about the human body, what do you think accounts for the high percentage of oxygen (65.0%)? The human body breathes in oxygen constantly, and because oxygen is a heavy element, it makes up a large percentage of body mass. The human body is made up mainly of water, and there is one oxygen atom in every water molecule. The human body is made up mainly of water, and there are two oxygen atoms in every water molecule. The human body breathes in oxygen constantly, and oxygen in the blood and tissues makes up a large percentage of body mass.

The human body is made up mainly of water, and there is one oxygen atom in every water molecule. The human body is mostly made up of water (H2O), and there is one oxygen atom in each molecule of water. Note that, although each water molecule also contains two hydrogen atoms, the atomic mass of hydrogen (about 1) is much smaller than the atomic mass of oxygen (about 16). Because of this, hydrogen contributes less to human body mass than oxygen.

from, out of, remove

de-

A(n) _____ bond joins these two oxygen atoms. quadruple covalent ionic double covalent hydrogen single covalent

double covalent

The brackets are indicating a(n) _____ bond. ionic hydrophobic single (nonpolar) covalent hydrogen polar covalent

hydrogen A hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.

fat

lip-

Which of the following is a trace element required by most living organisms? nitrogen oxygen hydrogen magnesium carbon

magnesium By weight, magnesium accounts for only 0.1% of most living things.

An ionic bond is formed when _____. both atoms are electrically neutral atoms are subjected to radioactive isotopes both atoms are nonpolar one atom transfers an electron to another atom both atoms are equally attractive to electrons

one atom transfers an electron to another atom Transfer of an electron from one atom to another results in a positive ion (cation) and a negative ion (anion), which usually attract each other to form an ionic bond. However, the ions need not have acquired their electrical charge due to an electron transfer with each other.

Changing the number of _____ would change an atom into an atom of a different element. electrons circling the nucleus of an atom bonds formed by an atom particles in the nucleus of an atom protons in an atom neutrons in an atom

protons in an atom Atoms of each element have a unique number of protons within their nuclei. Changing the number of protons in an atom occurs only in nuclear reactions, not chemical reactions.

four

quad- quat-

not

non-

Hydrogen bonding is most often seen _____. when multiple carbon atoms are present in molecules whose three-dimensional shape is tetrahedral when the bonds within the molecule are nonpolar covalent bonds when hydrogen is covalently bonded to an electronegative atom if the molecule consists of three or fewer atoms

when hydrogen is covalently bonded to an electronegative atom Highly electronegative atoms attract shared electrons more strongly than hydrogen does, resulting in a slight positive charge on the hydrogen atom. The slightly positive hydrogen atom is then attracted to another electronegative atom, forming a hydrogen bond.