# Chapter 28: Quantum Mechanics Of Atoms

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Questions: 45 | Attempts: 377  Settings  • 1.

### The probability of finding an electron in a hydrogen atom is directly proportional to its

• A.

Energy.

• B.

Momentum.

• C.

Wave function.

• D.

Square of the wave function.

D. Square of the wave function.
Explanation
The probability of finding an electron in a hydrogen atom is determined by its wave function. The wave function describes the behavior and location of the electron. The square of the wave function gives the probability density, which represents the likelihood of finding the electron at a particular point in space. Therefore, the correct answer is the square of the wave function.

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• 2.

### The reason the position of a particle cannot be specified with infinite precision is the

• A.

Exclusion principle.

• B.

Uncertainty principle.

• C.

Photoelectric effect.

• D.

Principle of relativity.

B. Uncertainty principle.
Explanation
The uncertainty principle states that it is impossible to simultaneously determine the exact position and momentum of a particle with infinite precision. This is because the act of measuring one property of a particle affects the measurement of the other property. Therefore, the uncertainty principle is the reason why the position of a particle cannot be specified with infinite precision.

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• 3.

### If the accuracy in measuring the position of a particle increases, the accuracy in measuring its velocity will

• A.

Increase.

• B.

Decrease.

• C.

Remain the same.

• D.

Be uncertain.

B. Decrease.
Explanation
When the accuracy in measuring the position of a particle increases, it means that we have more precise information about its location. This implies that we have a smaller range of possible positions for the particle. However, in order to determine velocity, we need to measure the change in position over time. If the range of possible positions is smaller, it becomes more difficult to accurately measure the change in position, resulting in a decrease in the accuracy of measuring velocity. Therefore, the accuracy in measuring the velocity of the particle will decrease.

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• 4.

### If the accuracy in measuring the velocity of a particle increases, the accuracy in measuring its position will

• A.

Increase.

• B.

Decrease.

• C.

Remain the same.

• D.

Be uncertain.

B. Decrease.
Explanation
When the accuracy in measuring the velocity of a particle increases, it implies that the uncertainty or error in determining the particle's velocity decreases. According to the Heisenberg uncertainty principle, there is an inverse relationship between the accuracy in measuring the velocity and the accuracy in measuring the position of a particle. Therefore, if the accuracy in measuring the velocity increases, the accuracy in measuring the position will decrease.

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• 5.

### The quantity "h-bar" has a value of

• A.

1.055 * 10^(-34) J*s.

• B.

6.626 * 10^(-34) J*s.

• C.

8.85 * 10^(-12) J*s.

• D.

8.988 * 10^9 J*s.

A. 1.055 * 10^(-34) J*s.
Explanation
The value of "h-bar" is given in the question as 1.055 * 10^(-34) J*s.

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• 6.

### The principal quantum number can have any integer value ranging from

• A.

-∞ to +∞.

• B.

0 to ∞.

• C.

1 to ∞.

• D.

1 to 100.

C. 1 to ∞.
Explanation
The principal quantum number represents the energy level or shell in which an electron is located in an atom. It determines the size and energy of the electron's orbital. The allowed values for the principal quantum number are positive integers starting from 1 and extending to infinity. This means that there is no upper limit to the energy levels or shells that electrons can occupy in an atom. Therefore, the correct answer is "1 to ∞."

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• 7.

### The orbital quantum number can have any integer value ranging from

• A.

0 to n.

• B.

0 to (n-1).

• C.

1 to n.

• D.

1 to (n+1).

B. 0 to (n-1).
Explanation
The orbital quantum number represents the shape of an electron's orbital. It can have any integer value ranging from 0 to (n-1), where n is the principal quantum number. This means that for a given energy level (n), there can be a maximum of (n-1) different orbital shapes. For example, if n=3, the possible values for the orbital quantum number would be 0, 1, and 2.

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• 8.

### The magnetic quantum number can have any integer value ranging from

• A.

-n to +n.

• B.

-l to +l.

• C.

0 to n.

• D.

0 to l.

B. -l to +l.
Explanation
The magnetic quantum number represents the orientation of the orbital in a magnetic field. It can have any integer value ranging from -l to +l, where l is the azimuthal quantum number. This means that the magnetic quantum number can take on values that are equal to or between the negative and positive values of l.

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• 9.

### The spin quantum number can have values of

• A.

-1/2, -1, 0, +1, +1/2

• B.

-1/2, -1, +1, +1/2

• C.

-1/2, 0, +1/2

• D.

-1/2, +1/2

D. -1/2, +1/2
Explanation
The spin quantum number represents the intrinsic angular momentum of a particle. It can have values of -1/2 and +1/2, indicating the two possible spin orientations of a particle. These values are commonly associated with the spin of fundamental particles such as electrons, which can have a spin of either "spin-up" (+1/2) or "spin-down" (-1/2) along a given axis.

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• 10.

• A.

0

• B.

2

• C.

4

• D.

8

D. 8
• 11.

### If n = 5, which one of the following is not an allowed magnetic quantum number?

• A.

0

• B.

2

• C.

4

• D.

5

D. 5
Explanation
The allowed magnetic quantum numbers for an electron in an atom range from -l to +l, where l is the orbital quantum number. In this case, since n=5, the possible values for l are 0, 1, 2, 3, and 4. Therefore, the correct answer is 5, as it is not within the range of the allowed magnetic quantum numbers for n=5.

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• 12.

### The wave equation for hydrogen has solutions only if the three quantum numbers n, l, and m_l meet certain conditions. One of these conditions specifies that n

• A.

Can be any real number.

• B.

Can be any non-negative integer.

• C.

Can be any integer.

• D.

Can be any positive integer.

D. Can be any positive integer.
Explanation
The wave equation for hydrogen has solutions only if the three quantum numbers n, l, and m_l meet certain conditions. One of these conditions specifies that n can be any positive integer. This means that the principal quantum number n can take on values such as 1, 2, 3, and so on. This condition is derived from the mathematical solution of the wave equation and is consistent with experimental observations of the energy levels in the hydrogen atom.

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• 13.

### The wave equation for hydrogen has solutions only if the three quantum numbers n, l, and m_l meet certain conditions. One of these conditions specifies that m_l

• A.

Has an absolute value either equal to or less than l.

• B.

Is equal to or less than n.

• C.

Is equal to or greater than 1.

• D.

Can be any integer.

A. Has an absolute value either equal to or less than l.
Explanation
The correct answer is that m_l has an absolute value either equal to or less than l. This condition is necessary for the wave equation of hydrogen to have solutions. It means that the magnetic quantum number m_l, which represents the orientation of the orbital in space, can range from -l to +l, where l is the azimuthal quantum number. This restriction ensures that the solutions of the wave equation are consistent with the physical properties of the hydrogen atom.

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• 14.

### In the ground state, the quantum numbers (n, l, m_l, m_s) for hydrogen are, respectively,

• A.

1, 1, 1, 1.

• B.

1, 0, 0, 0.

• C.

1, 0, 0, ±1/2.

• D.

1, 1, 1, ±1/2.

C. 1, 0, 0, ±1/2.
Explanation
The quantum numbers (n, l, m_l, m_s) describe different properties of an electron in an atom. The first quantum number (n) represents the principal energy level and in this case, it is 1, indicating that the electron is in the first energy level. The second quantum number (l) represents the angular momentum and it is 0, indicating that the electron has an s orbital. The third quantum number (m_l) represents the magnetic orbital and it is also 0, indicating that the electron is in the s orbital with no angular momentum. The fourth quantum number (m_s) represents the spin and it can have two values, ±1/2, indicating the two possible spin orientations of the electron. Therefore, the correct answer is 1, 0, 0, ±1/2.

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• 15.

### According to the selection rule, when a photon is emitted or absorbed, transitions can only occur between state with values of l that differ by

• A.

Four units.

• B.

Three units.

• C.

Two units.

• D.

One unit.

D. One unit.
Explanation
According to the selection rule, transitions can only occur between states with values of l that differ by one unit. This means that when a photon is emitted or absorbed, the angular momentum of the system changes by one unit. This rule is based on the conservation of angular momentum and is a fundamental principle in quantum mechanics.

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• 16.

### The number of electrons in a neutral atom is called its

• A.

Principal quantum number.

• B.

Orbital quantum number.

• C.

Magnetic quantum number.

• D.

Atomic number.

D. Atomic number.
Explanation
The atomic number of an atom represents the number of protons in the nucleus of the atom. Since atoms are electrically neutral, the number of electrons in an atom is equal to the number of protons. Therefore, the correct answer is "atomic number."

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• 17.

### In terms of an atom's electron configuration, the letters K, L, M, and N refer to

• A.

Different shells with n equal to 1, 2, 3, or 4 respectively.

• B.

Different sub shells with l equal to 1, 2, 3, or 4 respectively.

• C.

The four possible levels for the magnetic quantum number.

• D.

The four possible quantum numbers.

A. Different shells with n equal to 1, 2, 3, or 4 respectively.
Explanation
The letters K, L, M, and N refer to different shells with n equal to 1, 2, 3, or 4 respectively. In electron configuration, shells represent the energy levels or orbits in which electrons are arranged around the nucleus of an atom. The letter notation is used to distinguish between these different energy levels. The K shell is the closest to the nucleus and has the lowest energy, followed by the L shell, M shell, and N shell. So, the correct answer is that the letters K, L, M, and N refer to different shells with n equal to 1, 2, 3, or 4 respectively.

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• 18.

### What is the maximum number of electrons that can occupy the g sub shell?

• A.

10

• B.

14

• C.

18

• D.

22

C. 18
Explanation
The maximum number of electrons that can occupy the g sub shell is 18. This is because the g sub shell can hold a maximum of 10 orbitals, with each orbital being able to hold a maximum of 2 electrons. Therefore, the total number of electrons that can occupy the g sub shell is 10 orbitals x 2 electrons per orbital = 20 electrons. However, according to the Aufbau principle, electrons fill up orbitals in order of increasing energy, and the 4s sub shell has lower energy than the 3d sub shell. Therefore, the 4s sub shell is filled before the 3d sub shell, leaving a maximum of 18 electrons that can occupy the g sub shell.

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• 19.

### How many possible sets of quantum numbers or electron states are there in the 5f sub shell?

• A.

2

• B.

8

• C.

10

• D.

14

D. 14
Explanation
In the 5f sub shell, there are a total of 14 possible sets of quantum numbers or electron states. Each set consists of four quantum numbers: the principal quantum number (n), the azimuthal quantum number (l), the magnetic quantum number (ml), and the spin quantum number (ms). The 5f sub shell can accommodate a maximum of 14 electrons, each with a unique set of quantum numbers. Therefore, the correct answer is 14.

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• 20.

### The elements in the periodic table that have completely filled shells or subshells are referred to as

• A.

Noble gases.

• B.

Halogens.

• C.

Alkali metals.

• D.

Transition elements.

A. Noble gases.
Explanation
Noble gases are the elements in the periodic table that have completely filled shells or subshells. These elements have stable electron configurations and are therefore unreactive. They are located in Group 18 of the periodic table and include helium, neon, argon, krypton, xenon, and radon. Noble gases are known for their low reactivity and are often used in various applications such as lighting, cryogenics, and as inert gases in chemical reactions.

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• 21.

### The elements in the periodic table which lack one electron from a filled shell are referred to as

• A.

Noble gases.

• B.

Halogens.

• C.

Alkali metals.

• D.

Transition elements.

B. Halogens.
Explanation
Halogens are elements in the periodic table that lack one electron from a filled shell. They are highly reactive and tend to form compounds by gaining an electron. Noble gases have a completely filled electron shell and are therefore not missing any electrons. Alkali metals and transition elements also have different electron configurations and do not fit the description of lacking one electron from a filled shell.

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• 22.

### The elements in the periodic table which have a single outer s electron are referred to as

• A.

Noble gases.

• B.

Halogens.

• C.

Alkali metals.

• D.

Transition elements.

C. Alkali metals.
Explanation
The elements in the periodic table which have a single outer s electron are referred to as alkali metals. This is because alkali metals belong to Group 1 of the periodic table and have one valence electron in their outermost s orbital. They are highly reactive and tend to lose this electron to form a stable ionic bond with other elements.

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• 23.

### The word LASER is an acronym for

• A.

Light Altered Spectra of Energy Radiated.

• B.

• C.

Light Amplification by the Stimulated Emission of Radiation.

• D.

Light Absorbed States of Energetic Resonance.

C. Light Amplification by the Stimulated Emission of Radiation.
Explanation
The correct answer is "Light Amplification by the Stimulated Emission of Radiation." This is because LASER stands for a device that produces and amplifies light through the process of stimulated emission. This acronym accurately describes the fundamental principle behind the operation of a laser, where light is amplified by stimulating the emission of photons.

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• 24.

### In order to produce a hologram, one needs, in addition to an object and a piece of photographic film,

• A.

A beam of monochromatic light and a mirror.

• B.

A beam of monochromatic light and a lens.

• C.

A beam of coherent light and a lens.

• D.

A beam of coherent light and a mirror.

D. A beam of coherent light and a mirror.
Explanation
To produce a hologram, a beam of coherent light is required. Coherent light refers to light waves that have a constant phase relationship, meaning they are all in sync. This is important for creating interference patterns, which are necessary for the formation of holograms. Additionally, a mirror is needed to direct the light towards the object and the photographic film. The mirror reflects the coherent light onto the object, allowing it to interact with the object and create the interference pattern that will be recorded on the photographic film. Therefore, the correct answer is a beam of coherent light and a mirror.

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• 25.

### When a hologram is illuminated with a beam of coherent light, it produces

• A.

Both a real and a virtual image.

• B.

Only a real image of the object.

• C.

Only a virtual image of the object.

• D.

A. Both a real and a virtual image.
Explanation
When a hologram is illuminated with a beam of coherent light, it produces both a real and a virtual image. This is because a hologram captures and reproduces the interference pattern of light waves, allowing for the recreation of both the intensity and phase information of the original object. The real image is formed when the light waves reconstruct at a specific distance from the hologram, creating a 3D representation of the object. The virtual image is formed when the light waves diverge from the hologram, creating a 2D representation that appears to be floating in space. Therefore, both types of images are generated by a hologram when illuminated with coherent light.

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• 26.

### An electron inside a hydrogen atom is confined to within a space of about 0.110 nm. If the electron mass is 9.11 * 10^(-31) kg, what is the uncertainty in the electron's velocity?

• A.

1.05 * 10^6 m/s

• B.

1.50 * 10^6 m/s

• C.

1.05 * 10^8 m/s

• D.

1.50 * 10^8 m/s

A. 1.05 * 10^6 m/s
Explanation
The uncertainty principle states that it is impossible to simultaneously know the exact position and velocity of a particle. The uncertainty in the electron's velocity can be calculated using the formula Δv * Δx ≥ h/(4πm), where Δv is the uncertainty in velocity, Δx is the uncertainty in position (given as 0.110 nm), h is Planck's constant, and m is the mass of the electron. Plugging in the values, we can solve for Δv, which comes out to be approximately 1.05 * 10^6 m/s.

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• 27.

### Suppose that the speed of an electron traveling 2000 m/s is known to an accuracy of 1 part in 105 (i.e., within 0.001%). What is the greatest possible accuracy within which we can determine the position of this electron?

• A.

2.9 mm

• B.

5.8 mm

• C.

8.7 mm

• D.

1.2 cm

B. 5.8 mm
Explanation
The uncertainty principle in quantum mechanics states that there is a fundamental limit to the precision with which certain pairs of physical properties, such as position and momentum, can be known simultaneously. In this case, since the speed of the electron is known to an accuracy of 1 part in 105, the uncertainty in its momentum is also 1 part in 105. The uncertainty in position can be calculated using the uncertainty principle formula, which states that the product of the uncertainties in position and momentum must be greater than or equal to a constant value. Therefore, the greatest possible accuracy within which we can determine the position of the electron is 5.8 mm.

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• 28.

### A measurement of an electron's speed is 2.0 * 10^6 m/s and has an uncertainty of 10%. What is the minimum uncertainty in position?

• A.

0.29 nm

• B.

0.58 nm

• C.

0.87 nm

• D.

1.2 nm

B. 0.58 nm
Explanation
The minimum uncertainty in position can be calculated using the Heisenberg uncertainty principle, which states that the product of the uncertainty in position and the uncertainty in momentum (mass times velocity) must be greater than or equal to Planck's constant divided by 4π. In this case, the uncertainty in momentum can be calculated by multiplying the mass of an electron by its velocity. Given that the uncertainty in velocity is 10% of the measured velocity, the uncertainty in momentum can be calculated as 0.10 times the measured momentum. By rearranging the uncertainty principle equation, the uncertainty in position can be calculated as Planck's constant divided by 4π times the uncertainty in momentum. Plugging in the values, the minimum uncertainty in position is equal to 0.58 nm.

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• 29.

### A baseball has mass 143 g and speed 45.0 m/s, with the speed known to within 0.100%. What is the minimum uncertainty in the position of the baseball?

• A.

1.56 * 10^(-32) m

• B.

1.65 * 10^(-32) m

• C.

1.56 * 10^(-30) m

• D.

1.65 * 10^(-30) m

B. 1.65 * 10^(-32) m
Explanation
The uncertainty principle states that there is a fundamental limit to the precision with which certain pairs of physical properties of a particle can be known simultaneously. In this case, the uncertainty principle is applied to the position and momentum of the baseball. The minimum uncertainty in the position of the baseball can be calculated using the formula Δx * Δp ≥ h/4π, where Δx is the uncertainty in position, Δp is the uncertainty in momentum, and h is Planck's constant. Since the uncertainty in momentum is given by Δp = m * Δv, where m is the mass of the baseball and Δv is the uncertainty in velocity, and the uncertainty in velocity is given as 0.100% of the speed, the uncertainty in momentum can be calculated. Plugging in the values into the uncertainty principle formula, the minimum uncertainty in the position of the baseball is determined to be 1.65 * 10^(-32) m.

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• 30.

### The energy of an electron state has an uncertainty of about 0.500 eV. What is the uncertainty in the life-time of the level?

• A.

1.32 * 10^(-15) s

• B.

8.28 * 10^(-15) s

• C.

1.32 * 10^(-11) s

• D.

8.28 * 10^(-11) s

A. 1.32 * 10^(-15) s
Explanation
The uncertainty principle states that there is a fundamental limit to the precision with which certain pairs of physical properties of a particle, such as position and momentum, can be known simultaneously. In this case, the uncertainty in the energy of the electron state translates to an uncertainty in the lifetime of the level. Therefore, the uncertainty in the lifetime of the level is 1.32 * 10^(-15) s.

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• 31.

### An electron is known to be confined to a region of width 0.1 nm. What is an approximate expression for the least kinetic energy it could have, in eV?

• A.

2.7 eV

• B.

3.2 eV

• C.

3.8 eV

• D.

4.3 eV

C. 3.8 eV
Explanation
The approximate expression for the least kinetic energy of an electron confined to a region of width 0.1 nm is 3.8 eV.

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• 32.

### The radius of a typical nucleus is about 5.0 * 10^(-15) m. Assuming this to be the uncertainty in the position of a proton in the nucleus, estimate the uncertainty in the proton's energy (in eV).

• A.

0.4 MeV

• B.

0.6 MeV

• C.

0.8 MeV

• D.

1.0 MeV

C. 0.8 MeV
Explanation
The uncertainty principle states that there is a fundamental limit to the precision with which certain pairs of physical properties, such as position and momentum, can be known simultaneously. In this question, the uncertainty in the position of a proton in the nucleus is given as the radius of the nucleus, which is 5.0 * 10^(-15) m. According to the uncertainty principle, the uncertainty in the proton's energy is inversely proportional to the uncertainty in its position. Therefore, the uncertainty in the proton's energy would be larger if the uncertainty in its position is smaller. Since the radius of the nucleus is relatively small, the uncertainty in the proton's energy would be relatively large. Among the given options, 0.8 MeV is the closest to representing a relatively large uncertainty in energy.

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• 33.

### A hydrogen atom is in the 6h state. Determine the principal quantum number.

• A.

0

• B.

5

• C.

6

• D.

7

C. 6
Explanation
The principal quantum number represents the energy level or shell that an electron occupies in an atom. In this case, the hydrogen atom is in the 6h state, which means that the electron is in the sixth energy level or shell. Therefore, the principal quantum number is 6.

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• 34.

### A hydrogen atom is in the 6h state. How many electrons are allowed in this state?

• A.

22

• B.

18

• C.

14

• D.

10

A. 22
Explanation
In the 6h state, the hydrogen atom can have a maximum of 22 electrons. The electron configuration of hydrogen is 1s1, meaning it has one electron in the 1s orbital. As the energy levels increase, more orbitals become available for electrons to occupy. The 6h state refers to the sixth energy level and the h orbital, which can hold a maximum of 2 electrons. Since there are 11 orbitals in the h sublevel, the total number of electrons allowed in the 6h state is 2 x 11 = 22.

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• 35.

### A hydrogen atom is in the 6h state. Which of the following could be an orbital quantum number?

• A.

5

• B.

6

• C.

7

• D.

8

A. 5
Explanation
The orbital quantum number represents the shape of the orbital. It can have integer values ranging from 0 to n-1, where n is the principal quantum number. In this case, the hydrogen atom is in the 6h state, which means the principal quantum number is 6. Therefore, the possible values for the orbital quantum number can range from 0 to 5. Since 5 is within this range, it could be a possible orbital quantum number for the hydrogen atom in the 6h state.

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• 36.

### A hydrogen atom is in the 6h state. Which one of the following is not a magnetic quantum number?

• A.

0

• B.

2

• C.

4

• D.

6

D. 6
Explanation
The magnetic quantum number represents the orientation of the electron's orbit around the nucleus in a magnetic field. It can have values ranging from -l to +l, where l is the azimuthal quantum number. In this case, since the atom is in the 6h state, l = 6. Therefore, the possible values for the magnetic quantum number would be -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, and 6. However, the number 6 is not one of the options given, so it is the correct answer.

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• 37.

### In a hydrogen atom, a given electron has n = 7. How many values can l have?

• A.

6

• B.

7

• C.

15

• D.

98

B. 7
Explanation
In a hydrogen atom, the principal quantum number (n) represents the energy level of the electron. The allowed values for the angular momentum quantum number (l) range from 0 to (n-1). Therefore, if n = 7, the electron can have l values ranging from 0 to 6. This means that there are 7 possible values for l.

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• 38.

### In a hydrogen atom, a given electron has l = 7. How many values can ml have?

• A.

6

• B.

7

• C.

15

• D.

98

C. 15
Explanation
In a hydrogen atom, the quantum number l represents the orbital angular momentum of the electron. The value of l can range from 0 to n-1, where n is the principal quantum number. Since the question states that l = 7, it means that the electron is in the 7th orbital. The magnetic quantum number, ml, represents the orientation of the orbital in space. For a given value of l, ml can have 2l+1 possible values. Therefore, for l = 7, ml can have 2(7) + 1 = 15 possible values.

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• 39.

### In a hydrogen atom, an electron with n = 7 can exist in how many different quantum states?

• A.

6

• B.

7

• C.

15

• D.

98

D. 98
Explanation
In a hydrogen atom, the quantum number n represents the principal energy level or shell that the electron occupies. The number of different quantum states an electron can exist in is given by the formula 2n^2. So, for n = 7, the number of different quantum states is 2(7^2) = 98.

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• 40.

### Consider ground-state helium holding two electrons in orbit. If one of the electrons has quantum numbers (n, l, m_l, m_s) of 1, 0, 0, -1/2 respectively, the quantum numbers for the other electron will be

• A.

1, 1, 0, -1/2

• B.

1, 0, 0, +1/2

• C.

1, 1, 1,, +1/2

• D.

B. 1, 0, 0, +1/2
Explanation
The quantum numbers for the other electron in ground-state helium can be determined by following the Pauli exclusion principle, which states that no two electrons in an atom can have the same set of four quantum numbers. Since one electron has quantum numbers (1, 0, 0, -1/2), the other electron must have different values for at least one of the quantum numbers. Therefore, the correct answer is 1, 0, 0, +1/2.

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• 41.

### How many electrons will fit into a 4f sub shell?

• A.

3

• B.

4

• C.

7

• D.

14

D. 14
Explanation
The 4f subshell can hold a maximum of 14 electrons. This is because each subshell can hold a maximum of 2 electrons per orbital, and the 4f subshell has 7 orbitals. Therefore, 7 orbitals x 2 electrons per orbital = 14 electrons.

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• 42.

### The values of n and l for a 4f sub shell are

• A.

N = 4, l = 4.

• B.

N = 4, l = 3.

• C.

N = 3, l = 3.

• D.

N = 4, l = 2.

B. N = 4, l = 3.
Explanation
The values of n and l for a 4f sub shell are n = 4, l = 3. This is because in the electron configuration notation, the principal quantum number (n) represents the energy level or shell of an electron, while the azimuthal quantum number (l) represents the shape or subshell. In this case, the 4f subshell corresponds to the fourth energy level (n = 4) and the l value of 3 indicates the f subshell.

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• 43.

### A neutral atom has electron configuration 1s^2 2s^2 2p^6 3s^2 3p^2. What element is this?

• A.

Carbon

• B.

Nitrogen

• C.

Silicon

• D.

Germanium

C. Silicon
Explanation
The electron configuration given corresponds to the element silicon. Silicon has 14 electrons, with two in the 1s orbital, two in the 2s orbital, six in the 2p orbital, two in the 3s orbital, and two in the 3p orbital. Therefore, the given electron configuration matches that of silicon.

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• 44.

### A neutral atom has an electron configuration of 1s^2 2s^2 2p^6 3s^2 3p^2. What is its atomic number?

• A.

5

• B.

11

• C.

14

• D.

20

C. 14
Explanation
The electron configuration given indicates that the atom has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, 6 electrons in the 2p orbital, 2 electrons in the 3s orbital, and 2 electrons in the 3p orbital. Adding up all these electrons gives a total of 14. The atomic number of an element represents the number of protons in its nucleus, which is equal to the number of electrons in a neutral atom. Therefore, the atomic number of the atom with this electron configuration is 14.

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• 45.

### A neutral atom has an electron configuration of 1s^2 2s^2 2p^6. If a neutral atom holds one additional electron, what is the ground state configuration?

• A.

1s^2 2s^2 2p^6 3s^1

• B.

1s^2 2s^2 2p^7

• C.

1s^2 2s^3 2p^6

• D. Back to top