Mastering Biol_ Ch 2

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

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. mass number 16, atomic number 7. 7 electrons. 10 neutrons. All of the above.

10 neutrons

From its atomic number of 15, it is possible to predict that the phosphorus atom has _____. 15 neutrons and 15 protons 30 neutrons 5 neutrons, 5 protons, and 5 electrons 15 protons and 15 electrons 8 electrons in its outermost electron shell

15 protons and 15 electrons

How many electrons are involved in a single covalent bond? one two three four

2

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

2

This atom can form up to _____ single covalent bond(s).

4

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

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

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

6

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

All of the above. (Perfect! 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.)

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

are different ions

About twenty-five of the 92 natural elements are known to be essential to life. Which 4 of these 25 elements make up approximately 96 percent of living matter? carbon, hydrogen, nitrogen, oxygen carbon, oxygen, phosphorus, hydrogen carbon, oxygen, nitrogen, calcium oxygen, hydrogen, calcium, nitrogen carbon, sodium, hydrogen, nitrogen

carbon, hydrogen, nitrogen, oxygen

What type of bond is joining the two hydrogen atoms? hydrophobic hydrophilic ionic covalent hydrogen

covalent

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

double covalent

A phrase that applies to covalent bonding and not other kinds of bonds is ... electron-sharing. paired electrons. charge attraction. great strength. All of the above.

electron-sharing.

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

ionic

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 shouldn't have 3 electrons. no shell can hold more than 2 electrons. the first shell must fill before the second shell can have electrons. the second shell can't have 4 electrons. the second shell should have 8 electrons.

the first shell shouldn't have 3 electrons.

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

an attraction between ions of opposite charge

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

8 neutrons in the nucleus. (Good choice! The atomic number (7) gives the number of protons, and the mass number is the number of protons plus neutrons.)

Which drawing in the figure above depicts an atom with six valence electrons? A B C D E

C

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

C; it has 6 protons.

What is the difference between covalent bonds and ionic bonds? Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the sharing of protons between charged atoms. Covalent bonds require carbon whereas ionic bonds do not. Covalent bonds involve the transfer of electrons between charged atoms; ionic bonds involve the sharing of electrons between atoms. Covalent bonds involve the sharing of pairs of electrons between atoms; ionic bonds involve the sharing of single electrons between atoms. Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms.

Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms.

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

D

Which of the following statements most accurately describes the relative positions of the shared electrons in methane (CH4) and ammonia (NH3)? See Section 2.1 ( page 57) . Hints Electrons are shared equally in both molecules. Electrons are shared equally in NH3 and unequally in CH4. Electrons are shared unequally in both molecules. Electrons are shared equally in CH4 and unequally in NH3.

Electrons are shared equally in CH4 and unequally in NH3

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

Electrons determine the atom's size

For the element phosphorus, which statement is always true? See Section 2.1 ( page 57) . Hints Its nucleus contains 15 neutrons. Its nucleus contains 15 electrons. Its nucleus contains 15 protons. Its valence is 15.

Its nucleus contains 15 protons.

Why are covalent bonds between hydrogen and nitrogen or oxygen polar? See Section 2.1 ( page 57) . Hints Nitrogen and oxygen are more electronegative than hydrogen so electrons are shared unequally. Nitrogen and oxygen are more electronegative than hydrogen so electrons are shared equally. Nitrogen and oxygen are less electronegative than hydrogen so electrons are shared unequally. Nitrogen and oxygen are less electronegative than hydrogen so electrons are shared equally

Nitrogen and oxygen are more electronegative than hydrogen so electrons are shared unequally.

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

None of these. Elements are defined by the number of protons.

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

Probability model

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

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 isotopes. These atoms are different elements. These atoms are isomers.

These atoms are isotopes.

When the atoms involved in a covalent bond have the same electronegativity, what type of bond results? a nonpolar covalent bond a hydrogen bond a polar covalent bond an ionic bond

a nonpolar covalent bond

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

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

You need to write down information about a molecule, but need to indicate only the type and number of atoms it contains. Which representation would work best? ball-and-stick model structural formula space-filling model molecular formula

molecular formula

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

molecule

Bonds between two atoms that are equally electronegative are _____. hydrogen bonds van der Waals interactions nonpolar covalent bonds polar covalent bonds ionic bonds

nonpolar covalent bonds

A covalent bond is likely to be polar when _____. one of the atoms has absorbed more energy than the other atom the two atoms sharing electrons are the same elements the two atoms sharing electrons are equally electronegative one of the atoms sharing electrons is more electronegative than the other atom carbon is one of the two atoms sharing electrons

one of the atoms sharing electrons is more electronegative than the other atom

A covalent chemical bond is one in which _____. electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged outer-shell electrons of one atom are transferred to fill the inner electron shell of another atom outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals electrons from the same atom, but opposite spins, are paired protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms

outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals

Atoms of a specific element always have a constant number of _____. See Section 2.1 ( page 57) . Hints neutrons functional groups electrons protons

protons

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

single (nonpolar) covalent

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

the number of electrons in the outermost electron shell (An atom is least likely to participate in a reaction when its outermost shell is stable.)

Knowing the atomic mass of an element allows inferences about which of the following? the number of protons in the element the number of neutrons in the element the number of electrons in the element the number of protons plus neutrons in the element the number of protons plus electrons 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 particles in the nucleus. the same mass number. the same number of shells. the same number of protons.

the same number of protons. (You got it! The number of protons defines a chemical element. The number of neutrons and electrons can differ among atoms of the same element.)