jff lslfj

1. Physics for Scientists and Engineers, 6e
Chapter 42 - Atomic Physics

2. A hydrogen atom is in its ground state. Incident on
the atom are many photons each having an energy
of 10.5 eV. The result is that
1 2 3
33% 33%33%
1 2 3 4 5
1. the atom is excited to a
higher allowed state
2. the atom is ionized
3. the photons pass by the
atom without interaction

3. Because the energy of 10.5 eV does not
correspond to raising the atom from the ground
state to an allowed excited state, there is no
interaction between the photon and the atom.

4. When electrons collide with an atom, they can transfer some or
all of their energy to the atom. Suppose a hydrogen atom in its
ground state is struck by many electrons each having a kinetic
energy of 10.5 eV. The result is that
1 2 3
33% 33%33%
1 2 3 4 5
1. the atom is excited to a
higher allowed state and
the electrons pass by the
atom without interaction
2. the atom is ionized
3. the atom is excited to a
higher allowed state and
the atom is ionized

5. A hydrogen atom makes a transition from the n = 3
level to the n = 2 level. It then makes a transition
from the n = 2 level to the n = 1 level. Which
transition results in emission of the longest-
wavelength photon?
1 2 3
33% 33%33%
1 2 3 4 5
1. the first transition
2. the second transition
3. neither, because the
wavelengths are the
same for both transitions.

6. As the electrons strike the atom, they can give
up any amount of energy between 0 and 10.5
eV, unlike the photons in question 1, which
must give up all of their energy in one
interaction. Thus, those electrons that undergo
the appropriate collision with the atom can
transfer 13.606 eV – 3.401 eV = 10.205 eV to
the atom and excite it to the n = 2 state. Those
electrons that do not make the appropriate
collision will transfer only enough kinetic
energy to the atom as a whole to satisfy
conservation of momentum in the collision,
without raising the atom to an excited state.

7. The longest-wavelength photon is associated
with the lowest energy transition, which is n =
3 to n = 2.

8. How many possible subshells are there for the n = 4
level of hydrogen?
1 2 3 4 5
20% 20% 20%20%20%
1 2 3 4 5
1. 5
2. 4
3. 3
4. 2
5. 1

9. The number of subshells is the same as the
number of allowed values of ℓ. The allowed
values of ℓ for n = 4 are ℓ = 0, 1, 2, and 3,
so there are four subshells.

10. When the principal quantum number is n = 5, how
many different values of ℓ are possible?
1 2 3 4
25% 25%25%25%
1 2 3 4 5
1. 5
2. 6
3. 7
4. 9

11. Five values (0, 1, 2, 3, 4) of ℓ, as follows:

12. And when the principal quantum number is n = 5,
how many different values of mℓ are possible?
1 2 3 4
25% 25%25%25%
1 2 3 4 5
1. 5
2. 6
3. 7
4. 9

13. Nine different values (–4, –3, –2, –1, 0, 1, 2,
3, 4) of mℓ
, as follows:

14. In the hydrogen atom, the quantum number n can
increase without limit. Because of this, the frequency
of possible spectral lines from hydrogen also
increases without limit.
1 2
50%50%
1 2 3 4 5
1. true
2. false

15. If the energy of the hydrogen atom were
proportional to n (or any power of n), the
energy would become infinite as n grows to
infinity. But the energy of the atom is
inversely proportional to n2
. Thus, as n
increases to very large values, the energy of
the atom approaches zero from the negative
side. As a result, the maximum frequency of
emitted radiation approaches a value
determined by the difference in energy
between zero and the (negative) energy of
the ground state.

16. Rank the energy necessary to remove the
outermost electron from the following three
elements, smallest to largest:
1 2 3 4 5
20% 20% 20%20%20%
1 2 3 4 5
1. helium, neon, argon
2. neon, argon, helium
3. argon, neon, helium
4. argon, helium, neon
5. helium, argon, neon

17. The higher the value of Z, the closer to zero is
the energy associated with the outermost
electron and the smaller is the ionization
energy.

18. In an x-ray tube, as you increase the energy of the
electrons striking the metal target, the wavelengths
of the characteristic x-rays
1 2 3
33% 33%33%
1 2 3 4 5
1. increase
2. decrease
3. do not change

19. The wavelengths of the characteristic x-
rays are determined by the separation
between energy levels in the atoms of the
target, which is unrelated to the energy with
which electrons are fired at the target. The
only dependence is that the incoming
electrons must have enough energy to
eject an atomic electron from an inner shell.

20. It is possible for an x-ray spectrum to show the
continuous spectrum of x-rays without the presence
of the characteristic x-rays.
1 2
50%50%
1 2 3 4 5
1. true
2. false

21. If the electrons arrive at the target with very low
energy, atomic electrons cannot be ejected and
characteristic x-rays do not appear. Because the
incoming electrons experience accelerations, the
continuous spectrum appears.