Deck 19: The Nucleus and Nuclear Energy

Question 1

In nuclear fusion,

A) two smaller nuclei combine to form a larger nucleus.
B) many radioactive nuclei decay at once.
C) a large nucleus splits into smaller fragments.
D) the temperatures required are so high that it has never been accomplished on Earth.

Answer 1

two smaller nuclei combine to form a larger nucleus.

Question 2

What is the source of the energy released in nuclear reactions?

A) The binding of orbital electrons to the nuclear protons.
B) The conversion of mass to energy.
C) The conversion of nuclear kinetic energy to particle potential energy.
D) Heat released during the radioactive decay process.

Answer 2

The conversion of mass to energy.

Question 3

When a nucleus undergoes alpha decay, the daughter element always has

A) less charge than the parent.
B) the same atomic number as the parent.
C) more neutrons than the parent.
D) more electrons than the parent.

Answer 3

less charge than the parent.

Question 4

The discovery of the neutron helped people understand

A) how two atoms of the same element can have different atomic masses.
B) why the nucleus has a positive charge.
C) how electrons are attracted to the nucleus.
D) why the nucleus is much more massive than the electrons in an atom.

Question 5

The separation of different isotopes of a particular element can be difficult because

A) all isotopes are dangerous because of their radioactivity.
B) neutrons are so small.
C) chemical reactions happen the same way for the isotopes.
D) the masses of the isotopes are the same.

Question 6

In nuclear fission,

A) a nucleus is split into two less massive nuclei.
B) two heavy nuclei are induced to decay simultaneously.
C) high-energy particles are released from a nucleus that is at rest.
D) a nucleus is bombarded with another nucleus in order to induce an alpha decay.

Question 7

The "half-life" of a large collection of radioactive nuclei is

A) the number of nuclei that decay in 1 second.
B) the number of nuclei that remain after 1 second.
C) larger for heavy nuclei than for lighter nuclei.
D) the time for half of the collection to decay.

Question 8

A nucleus undergoes radioactive decay, emitting a gamma ray. Which of the following statements is true?

A) The daughter nucleus has more neutrons than the parent.
B) A nuclear proton changes into an electron-positron pair.
C) Both daughter and parent nuclei have the same atomic number.
D) The daughter nucleus is more massive than the parent.

Question 9

The number of protons in the nucleus of an atom determines

A) the half-life of the nucleus.
B) the density of the nucleus.
C) the atomic mass.
D) the number of neutrons in the nucleus.

Question 10

A primary waste product of nuclear reactors that are designed for only power generation is

A) enriched uranium.
B) graphite.
C) radioactive materials.
D) high-pressure steam.

Question 11

The "alpha" particle is

A) two electrons bound to two protons.
B) two protons bound to two neutrons.
C) an electron.
D) two electrons bound to two neutrons.
E) a photon.

Question 12

The three types of nuclear radiation are

A) protons, electrons, neutrons.
B) electrical, strong nuclear, weak nuclear.
C) radiation, convection, conduction.
D) gamma, beta, alpha.

Question 13

In a nuclear reactor, "chain reaction" refers primarily to

A) an out-of-control explosion.
B) the process of heating water to create steam to generate electric power.
C) the enrichment of uranium to make fuel for the reactor.
D) the process by which the fission of one nucleus causes other nuclei to undergo fission.

Question 14

The substance that comes from a nuclear reactor which is used to generate power is

A) enriched uranium.
B) high-pressure steam.
C) radioactive materials.
D) graphite.

Question 15

The word "radioactive" means

A) an atomic nucleus absorbs neutrons.
B) there is significant interference between atomic radiation and radio reception.
C) there are nuclei present which will spontaneously emit nuclear radiation.
D) an atom spontaneously captures an electron from a neighboring atom.

Question 16

Which of the following mechanisms can change the half-life of radioactive nuclei?

A) Increasing the number of nuclei in the sample
B) Extreme high pressure
C) Extreme high temperature
D) None of these

Question 17

A nucleus undergoes beta decay. Which of the following statements is true?

A) The daughter element has more protons than the parent.
B) The daughter element has fewer protons than the parent.
C) Both daughter and parent elements have the same atomic number.
D) The daughter element has the same number of protons as the parent.

Question 18

A "gamma" ray is

A) an electron.
B) electromagnetic radiation.
C) two electrons bound to two neutrons.
D) a helium nucleus.

Question 19

During radioactive decay, the daughter element is always

A) more massive than the parent.
B) the same mass as the parent.
C) less massive than the parent.
D) None of these.

Question 20

The "beta" particle is

A) an electron.
B) electromagnetic radiation.
C) two electrons bound to two neutrons.
D) a helium nucleus.

Question 21

Walther Bothe and Wilhelm Becker discovered a new kind of particle radiation in 1930. The particle was later determined to be a neutron. Bothe and Becker generated neutron radiation by

A) heating nuclei to extremely high temperatures to boil the neutrons off.
B) using an isotope that decays by emitting neutrons.
C) using electrons to attract protons away from the nucleus.
D) firing a beam of alpha particles at a beryllium target.

Question 22

Generally, the number of neutrons present in nuclei that are fission fragments is ________ the number of neutrons of corresponding nuclei of stable isotopes.

A) less than
B) equal to
C) greater than

Question 23

Energy released in a nuclear fission process is produced by

A) electrons moving from a higher energy orbit to a lower energy orbit.
B) the conversion of some charge to energy.
C) the conversion of gravitational potential energy into kinetic energy.
D) conversion of some mass to energy.

Question 24

Both conventional fossil fuel and nuclear power plants

A) produce waste heat that can affect the weather or upset the ecology of rivers or lakes.
B) produce carbon dioxide, which may increase global warming.
C) contribute to the problem of acid rain.
D) produce hazardous waste products that must be stored in isolation for thousands of years.

Question 25

The number of neutrons in a stable isotope must

A) equal the number of protons plus electrons.
B) equal the number of electrons.
C) equal the number of protons.
D) None of the choices is correct.

Question 26

Two atoms have the same number of neutrons but different numbers of protons. These two atoms

A) will exhibit different chemical properties.
B) are isotopes of each other.
C) have the same number of electrons.
D) have the same atomic mass.

Question 27

The average U.S. citizen receives measurable radiation from man-made sources such as power plants, medical and dental X-rays, and consumer products. The radiation received from natural sources is

A) about the same as that received from artificial sources.
B) almost immeasurable.
C) more than that received from artificial sources.
D) measurable but less than that received from artificial sources.

Question 28

The Tokamak is a type of

A) moderator used in pressurized heavy water reactors.
B) experimental fusion reactor.
C) nuclear reactor using graphite as a moderator, such as the reactor at Chernobyl.
D) particle accelerator.

Question 29

Two nuclei have the same number of protons but different numbers of neutrons. We call these two nuclei

A) isotopes.
B) isobars.
C) atomic mass units.
D) ions.

Question 30

The N¹⁴ nucleus consists of

A) 14 neutrons.
B) 14 protons.
C) 21 protons and 7 electrons.
D) 7 protons and 7 neutrons.

Question 31

A feature of the nuclear reactor at Chernobyl that contributed to the magnitude of the accident there was that

A) water was used only as a coolant, not a moderator.
B) plutonium could build up quickly in the reactor.
C) the uranium fuel was more highly enriched.
D) the reactor did not have control rods.

Question 32

In all nuclear reactions,

A) energy must be conserved.
B) the total number of protons plus neutrons must be conserved.
C) charge is not created or lost.
D) all of these.

Question 33

The primary reason that nuclear fusion has proven difficult to adapt for commercial power generation is that

A) the fuel is difficult to purify.
B) the possible fuel is scarce.
C) the temperatures involved are too low for efficient production.
D) nuclei repel each other due to their positive charges.

Question 34

In a nuclear fission reaction,

A) one nucleus splits into two equal halves.
B) one nucleus splits into two parts, neither daughter having a mass close to the parent.
C) one nucleus splits into two parts, one very small and one almost the same mass as the parent.
D) two nuclei combine to form a single, more massive nucleus.

Question 35

In a modern light water reactor, the ratio of U²³⁵ to U²³⁸ in the nuclear fuel is typically in the approximate ratio of

A) 0.7%.
B) 100%.
C) 11%.
D) 3%.
E) 67%.

Question 36

A deuterium nucleus and a tritium nucleus react to yield one alpha particle, a neutron, and energy. This is an example of a

A) chemical reaction.
B) fission reaction.
C) fusion reaction.
D) chain reaction.

Question 37

The purpose of the moderator in a reactor is to

A) slow neutrons down so that they will be more likely to initiate fission reactions.
B) provide cooling for the control rods.
C) reduce the number of neutrons available for the chain reaction.
D) separate the nuclear fuel from the spent products of fission.

Question 38

A deuterium nucleus and a tritium nucleus react to yield one alpha particle, a neutron, and energy. For this reaction, the sum of the masses of reaction products after the reaction is __________ the sum of the masses of particles before the reaction.

A) less than
B) equal to
C) greater than

Question 39

In a decay of ₉₀Th²³² by emission of an alpha particle, the daughter nucleus will be

A) "₉₂U²³²."
B) "₉₀Th²²⁸."
C) "₈₇Ac²³²."
D) "₈₈Ra²³⁰."
E) "₈₈Ra²²⁸."

Question 40

A sample of U²³⁵ that is below the critical mass will not sustain a chain reaction because

A) too many neutrons escape through the surface of the sample without initiating fission.
B) the inertia of the sample is too low for efficient fission.
C) nuclei repel each other due to their positive charges.
D) the heat produced by the spontaneous fission of some nuclei is insufficient.

Question 41

The atomic mass system is based upon

A) the mass of uranium-238, since it is the heaviest element occurring in nature.
B) the mass of the neutron.
C) the mass of liquid water.
D) the mass of carbon-12, a very common isotope of carbon.

Question 42

The instability of uranium-235 compared to uranium-238, along with the relative stability of hydrogen compared to tritium, shows that the stability of a given nucleus depends upon

A) the speed of electrons orbiting the nucleus: more mass means more gravitational pull.
B) adding or subtracting neutrons, which can change a stable isotope into an unstable isotope.
C) the mass: heavier nuclei are always less stable.
D) the number of electrons in the nucleus.

Question 43

Neutrons were discovered by James Chadwick by observing the behavior of

A) gold atoms in a thin foil.
B) copper conducting electricity in the absence of a magnetic field.
C) carbon dioxide molecules under high pressure.
D) the collision after-effects of protons emerging from paraffin.
Fill in the Blank Questions

Question 44

Momentum and energy from focused laser beams can be used in nuclear fusion. This is because

A) light cannot be melted, so its pressure can confine the reaction.
B) light is not magnetic.
C) light can also function as a moderator, like graphite or water in a uranium reactor.
D) the wavelength of light is small enough to penetrate each proton.

Question 45

To make a bomb based on the fission reaction work, one must at the time of detonation bring together an amount of fissionable material equal to or larger than the ____________ mass.

Question 46

Suppose a radioactive isotope has a half-life of 2.0 hours. For an initial sample of 6400 nuclei, the number remaining after 6.0 hours is about ________________.

Question 47

The nuclide ₉₃Np²³⁹ decays by emission of a negative electron. The daughter nucleus will have an atomic number ____________ and a mass number _______.

Question 48

A piece of uranium can be made into nuclear explosive only after it is purified into uranium-235, because

A) it has to be soldered with lead for safety.
B) the other naturally occurring isotopes of uranium interfere with efficient chain reactions.
C) uranium-235 is the heaviest isotope known to mankind.
D) before purification, the uranium-235 nucleus will not split apart.

Question 49

The atomic mass unit is based on the mass of the _________ atom.

Question 50

The energy radiated by the sun has as its primary origin energy produced by ____________ reactions.

Question 51

Materials that are used as moderators in nuclear power reactors are carbon (graphite) and _________________.

Question 52

The __________ was a particle predicted to exist long before it was observed because energy is not conserved in beta decays without it.

Question 53

Control rods are inserted into a nuclear reactor when you want the nuclear reaction rate to ____________ (two words).