# Atoms And Nuclei Quiz A

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This quiz is multiple choice which tests the participants’ conceptual knowledge about the topic 'Atoms and Nuclei'. The questions involve knowledge from four main sections including; The Structure of the Atom, The Structure of the Nucleus, Radioactivity and Nucleur Fission and Fusion.

• 1.

### Planck's constant has a value of

• A.

6.626 × 10^-34

• B.

1.055 × 10^34

• C.

8.988 × 10^-16

• D.

8.85 × 10^26

A. 6.626 × 10^-34
Explanation
Planck's constant, denoted by h, is a fundamental constant in quantum mechanics. It relates the energy of a photon to its frequency, and is used to calculate the energy levels of atoms and particles. The value of Planck's constant is approximately 6.626 × 10^-34 Joule-seconds (J·s). This means that for a given frequency, the energy of a photon is equal to the product of the frequency and Planck's constant. Planck's constant is an important constant in physics and is used in various calculations and equations.

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• 2.

### A photon is a particle that

• A.

Cannot travel in a vacuum.

• B.

Has zero electric charge.

• C.

Has zero magnetic field associated with it.

• D.

Has a velocity in a vacuum that varies with the photon frequency.

B. Has zero electric charge.
Explanation
A photon is a particle that has zero electric charge. This means that it is not affected by electric fields and does not interact with charged particles through electromagnetic forces. Photons are the fundamental particles of light and electromagnetic radiation, and their lack of electric charge allows them to travel freely through space and interact with other charged particles without being influenced by electric fields.

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• 3.

### What is the ionization energy of the neutral hydrogen atom?

• A.

6.8 eV

• B.

13.6 eV

• C.

27.2 eV

• D.

B. 13.6 eV
Explanation
The ionization energy of an atom is the amount of energy required to remove an electron from the atom. In the case of the hydrogen atom, the ionization energy is 13.6 eV. This value is a well-known and experimentally determined constant for hydrogen. It represents the energy needed to overcome the attractive force between the electron and the nucleus of the hydrogen atom and remove the electron completely.

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• 4.

### The wavelength of a ruby laser is 694.3 nm.  What is the energy difference between the two energy states involved in laseraction?

• A.

1.812 eV

• B.

1.646 eV

• C.

1.537 eV

• D.

1.790 eV

D. 1.790 eV
Explanation
The energy difference between two energy states can be calculated using the formula E = hc/λ, where E is the energy difference, h is Planck's constant, c is the speed of light, and λ is the wavelength. Plugging in the values, we get E = (6.626 x 10^-34 J s)(3 x 10^8 m/s)/(694.3 x 10^-9 m) = 2.856 x 10^-19 J. Converting this to electron volts (eV), we divide by 1.602 x 10^-19 J/eV to get E = 1.790 eV.

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• 5.

### An atom's atomic number is determined by the number of

• A.

Neutrons in its nucleus.

• B.

Alpha particles in its nucleus.

• C.

Protons in its nucleus.

• D.

Nucleons in its nucleus.

C. Protons in its nucleus.
Explanation
The atomic number of an atom is determined by the number of protons in its nucleus. The atomic number represents the number of protons in an atom, which defines its identity as a specific element. Neutrons and alpha particles do not contribute to the atomic number, although they are present in the nucleus. Nucleons is a general term that encompasses both protons and neutrons, so it is not the correct answer in this context.

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• 6.

### If an atom's atomic number is given by Z, its atomic mass by A, and its neutron number by N, which of the following is correct?

• A.

N = Z - A

• B.

N = A - Z

• C.

N = A + Z

• D.

B. N = A - Z
Explanation
The correct answer is N = A - Z. This equation represents the neutron number (N) of an atom, which is calculated by subtracting the atomic number (Z) from the atomic mass (A). This equation is based on the fact that the atomic mass of an atom is the sum of its protons and neutrons, and the atomic number represents the number of protons. Subtracting the atomic number from the atomic mass gives the number of neutrons in the atom.

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• 7.

### There is a limit to the size of a stable nucleus because of

• A.

The limited range of the strong nuclear force.

• B.

The weakness of the gravitational force.

• C.

The weakness of the electrostatic force.

• D.

A. The limited range of the strong nuclear force.
Explanation
The correct answer is the limited range of the strong nuclear force. The strong nuclear force is responsible for holding the protons and neutrons together in the nucleus of an atom. However, this force only acts over a short range, which means that as the nucleus gets larger, the force becomes weaker and cannot overcome the repulsive electrostatic forces between the positively charged protons. This results in an unstable nucleus, leading to radioactive decay or nuclear fission.

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• 8.

### When nucleons join to form a stable nucleus, energy is

• A.

Absorbed.

• B.

Not transferred.

• C.

Destroyed.

• D.

Released.

D. Released.
Explanation
When nucleons join to form a stable nucleus, energy is released. This is because the process of nuclear fusion, where nucleons combine to form a nucleus, involves the conversion of mass into energy according to Einstein's famous equation E=mc². The binding energy, which is the energy required to hold the nucleus together, is released in the form of electromagnetic radiation or kinetic energy. This release of energy is what powers the sun and other stars, as well as nuclear reactors on Earth.

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• 9.

### The binding energy per nucleon

• A.

Decreases steadily as we go to heavier elements.

• B.

Has a maximum near iron in the periodic table.

• C.

Is approximately constant throughout the periodic table, except for very light nuclei.

• D.

Increases steadily as we go to heavier elements.

B. Has a maximum near iron in the periodic table.
Explanation
As we go to heavier elements in the periodic table, the binding energy per nucleon decreases steadily. However, near iron, there is a peak in the binding energy per nucleon, making it the element with the highest binding energy per nucleon in the periodic table. This is due to the balance between the strong nuclear force, which holds the nucleus together, and the electrostatic repulsion between protons, which tends to push the nucleus apart. Near iron, this balance is optimal, resulting in a higher binding energy per nucleon.

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• 10.

### An alpha particle will be attracted to a

• A.

Proton.

• B.

Gamma ray.

• C.

Positive charge.

• D.

Negative charge.

D. Negative charge.
Explanation
An alpha particle is a positively charged particle consisting of two protons and two neutrons. According to the principle of electrostatics, opposite charges attract each other. Therefore, an alpha particle, being positively charged, will be attracted to a negative charge.

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• 11.

### When a gamma ray is emitted from an unstable nucleus,

• A.

The number of neutrons drops by one and the number of protons increases by one.

• B.

There is no change in either the number of neutrons or the number of protons.

• C.

The number of neutrons and the number of protons drop by two.

• D.

B. There is no change in either the number of neutrons or the number of protons.
Explanation
When a gamma ray is emitted from an unstable nucleus, it does not result in any change in the number of neutrons or protons. Gamma rays are high-energy photons and do not carry any charge or mass. Therefore, they do not affect the composition of the nucleus and the number of particles remains the same.

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• 12.

### The atomic number and mass number for calcium 39 are 20 and 39, respectively.  How many protons are in one atom?

• A.

20

• B.

39

• C.

1

• D.

19

A. 20
Explanation
The atomic number of an element represents the number of protons in its nucleus. Since the atomic number for calcium 39 is given as 20, it means that there are 20 protons in one atom of calcium 39.

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• 13.

### If 4.0 × 1018 atoms decay with a half-life of 2.3 years, how many are remaining after 3.7 years?

• A.

1.1 ×1018

• B.

1.3 × 1018

• C.

2.5 × 1018

• D.

1.7 × 1018

B. 1.3 × 1018
Explanation
The half-life of a substance is the amount of time it takes for half of the initial quantity to decay. In this case, the half-life is 2.3 years. After 3.7 years, which is longer than one half-life, more than half of the atoms will have decayed. Therefore, the remaining amount will be less than half of the initial quantity. The answer of 1.3 × 1018 is the closest option to being less than half of the initial quantity, making it the most reasonable answer.

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• 14.

### In a nuclear reaction, what value is conserved in addition to electric charge, energy, and momentum?

• A.

Atomic number

• B.

Nucleon number

• C.

Neutron number

• D.

B. Nucleon number
Explanation
In a nuclear reaction, the nucleon number is conserved in addition to electric charge, energy, and momentum. The nucleon number refers to the total number of protons and neutrons in the nucleus of an atom. During a nuclear reaction, the total number of nucleons before and after the reaction remains the same, indicating that the nucleon number is conserved. This conservation principle helps to explain the stability and behavior of atomic nuclei during nuclear reactions.

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• 15.

### A nuclear reaction is said to be exothermic if the total kinetic energy is

• A.

Zero after the reaction.

• B.

Equal both before and after the reaction

• C.

Less after the reaction than before.

• D.

Greater after the reaction than before.

D. Greater after the reaction than before.
Explanation
An exothermic nuclear reaction is one in which the total kinetic energy is greater after the reaction than before. This means that the reaction releases more energy than it absorbs, resulting in an increase in kinetic energy.

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• 16.

### The fuel for nuclear fission is

• A.

He.

• B.

U.

• C.

H.

• D.

B. U.
Explanation
The correct answer is U, which stands for uranium. Uranium is the fuel used in nuclear fission reactions. It is a radioactive material that can undergo a chain reaction, releasing a large amount of energy. Other radioactive materials can also be used as fuel for nuclear fission, but uranium is the most commonly used and widely available.

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• 17.

### What is the meaning of the term "critical mass"?

• A.

This refers to the minimum amount of fissionable material required to sustain a chain reaction.

• B.

This refers to the mass of the "critical" elements in a reactor, i.e., the uranium or plutonium.

• C.

This is the material which is just on the verge of becoming radioactive.

• D.

This is the amount of mass needed to make a power reactor economically feasible.

A. This refers to the minimum amount of fissionable material required to sustain a chain reaction.
Explanation
Critical mass refers to the minimum amount of fissionable material required to sustain a chain reaction. In other words, it is the threshold at which a nuclear reaction becomes self-sustaining.

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• 18.

### What is necessary to stop beta particles?

• A.

Metal foil

• B.

Air alone

• C.

Paper

• D.

Thick metal

A. Metal foil
Explanation
Metal foil is necessary to stop beta particles. Beta particles are high-energy electrons or positrons that can penetrate through materials to varying degrees depending on their energy. Metal foil, with its high density and atomic number, provides a greater number of atoms for the beta particles to interact with, resulting in a higher chance of absorption and stopping the particles. Air alone and paper are not dense enough to effectively stop beta particles, while thick metal may be excessive and unnecessary for stopping them.

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• 19.

### The fission reaction 235U + 1n → 141Ba + 92Kr + neutrons, the number of neutrons produced is

• A.

1

• B.

Zero

• C.

3

• D.

2

C. 3
Explanation
In a fission reaction, when a uranium-235 atom absorbs a neutron, it becomes highly unstable and splits into two smaller atoms, barium-141 and krypton-92. Along with these two smaller atoms, three neutrons are also produced. These neutrons can go on to collide with other uranium-235 atoms, causing a chain reaction and releasing more energy. Therefore, the correct answer is 3.

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• 20.

### What is the energy released (positive) or absorbed (negative) in the following reaction?  3H (3.016049)  +   3H  (3.016049)    =   4He (4.002603)   +    2(1n) (1.008665)

• A.

0.0122 MeV

• B.

-11.3 MeV

• C.

-0.0122 MeV

• D.

11.3 MeV