Mastering Biology Questions Chapter 2 (Exam 1)

The innermost electron shell of an atom can hold up to _____ electrons. a. 2 b. 8 c. 18 d. 32 e. 1

a

An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule? a. 2 b. 5 c. 1 d. 3 e. 4

c

Chemical reactions do not create or destroy matter but simply rearrange it. Which example is the correct completed equation for this reaction? 4 NH3 + _____ O2 → _____ NO + _____ H2O a. 4 NH3 + 1 O2 → 2 NO + 5 H2O b. 4 NH3 + 5 O2 → 2 NO + 1 H2O c. 4 NH3 + 5 O2 → 4 NO + 6 H2O d. 4 NH3 + 6 O2 → 4 NO + 5 H2O

c

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

c

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

a

True or False: Ions may form by transferring an atomic nucleus (with or without electrons) to another molecule. a. True b. False

a

What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons? a. 6 b. 12 c. 0 d. -1 e. 18

a

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

b

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

b

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero? a. The charge isn't near zero; it's -2. b. Shared electrons aren't always near oxygen. c. The valence shell has 6 electrons. d. The atom lost electrons from other shells. e. The atom has 8 electrons.

b

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

b

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

b

Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true? a. The bonds orient like tripods or pyramids. b. All the atoms lie in a plane. c. All the atoms lie in a line. d. The bonds orient in a tetrahedral fashion. e. The groups rotate around the C=C bond.

b

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds? a. The carbon nucleus has 4 protons. b. The valence shell needs 8 electrons. c. The first electron shell has 4 orbitals. d. All of the above. e. None of the above; carbon makes 3 covalent bonds.

b

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

b

A positive ion with two units of charge has 10 neutrons and 8 protons. The ion also has ... a. 8 electrons b. 16 electrons c. 6 electrons d. 10 electrons e. 12 electrons

c

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

c

The ammonia molecule (NH3) in the diagram has the observed bond orientation because ... a. N has four pairs of electrons in the valence shell. b. N has 7 protons in its nucleus. c. electrons repel one another. d. All of the above. e. None of the above.

d

The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium? a. an atom with 20 protons, 20 neutrons, and 18 electrons b. an atom with 21 protons, 20 neutrons, and 21 electrons c. an atom with 18 protons, 20 neutrons, and 18 electrons d. an atom with 20 protons, 21 neutrons, and 20 electrons

d

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ... a. 8 electrons. b. 3 electrons. c. 1 electron. d. 2 electrons. e. Can't tell without knowing which element it is.

d

What type of bond is joining the two hydrogen atoms? a. ionic b. hydrophobic c. hydrophilic d. covalent e. hydrogen

d

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

e

An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and its mass number, respectively, are ____. a. 8 and 17 b. 8 and 16 c. 9 and 17 d. 9 and 16

a

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

a

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

a

Which of the following substances is a compound? a. sodium b. liquid nitrogen c. hydrogen gas d. sugar

d

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

d

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

b

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

b

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

b

An atom's atomic number is 7. Its valence is most likely ... a. 2 b. 7 c. 3 d. 1 e. 5

c

Covalent bonds can occur where atoms share one or more pairs of electrons. Which of the following would form a double covalent bond? a. NaCl b. NH3 c. CO2 d. Cl2

c

In a double covalent bond, a carbon atom shares ... a. electrons in two of its shells b. two electrons c. electrons in two orbitals d. both valence and nonvalence electrons e. none of the above

c

In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively. a. 2, 1, 3, 4 b. 3, 2, 1, 4 c. 4, 1, 2, 3 d. 4, 1, 3, 2 e. 3, 2, 4, 2

c

In salt, what is the nature of the bond between sodium and chlorine? a. hydrophobic b. nonpolar covalent c. ionic d. polar covalent e. hydrogen

c

Which of the following subatomic particles contributes toward the atomic mass of hydrogen? a. element b. neutron c. proton d. electron

c

Covalent bonds hold atoms together because they ... a. (a) fill shells without giving atoms much charge. b. (b) bring electrons closer to protons. c. (c) use forces between nuclei as well as forces between electrons. d. do all of the above. e. do both (a) and (b).

e

Partial charges occur when ... a. (a) a covalent bond links atoms of two kinds. b. (b) atoms share electrons unequally. c. (c) two ions are close together. d. any of the above occur. e. both (a) and (b).

e

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

e

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

e

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

e