UCLA Chem 14A Thinkwell Quiz 2 (Modern Atomic Theory).

What are the permissible values for the angular quantum number (l) when n = 2?

0, 1

What are the permissible values for the angular quantum number (l) when n = 3?

0, 1, 2

What is the wavelength of an electron with a velocity of 6.7 × 107 m / s? (The mass of an electron is 9.109 × 10−31 kg.)

1.1 × 10−11 m

Suppose a beam of neutrons is fired at a crystal that has a spacing of 0.215 nm between atoms. Photographic film is used to record the places where the neutrons come through the crystal. Which of the following is the best estimate of the slowest speed at which the neutrons can be fired at the crystal and still result in an interference pattern on the film? (The mass of a neutron is 1.67 × 10−27 kg.)

1.85 × 103 m / s

What is the ground state electron configuration for fluorine?

1s2 2s2 2p5

What is the ground state electron configuration for boron?

1s22s22p1

What is the ground state electron configuration for oxygen?

1s22s22p4

What is the electron configuration of the oxide ion (O2− )?

1s22s22p6

How many angular nodes do the d orbitals have?

2

An atom of helium has a de Broglie wavelength of 4.3 × 10−12 meters. What is its velocity?

2.3 × 104 m / s

A string that is restricted at both ends has a length of 1.50 m. What is the wavelength of the string's fundamental frequency?

3.00 m

A metal begins to emit electrons, as measured in an apparatus similar to the one Hertz used, when exposed to light at a wavelength of 342 nm (ultraviolet). What is the work function of this metal?

3.63 eV

A string has a length of 84 cm. The string is stretched taut, and both ends are restricted to be nonmoving. Touching the string at which of the following points will not produce a standing wave when the string is plucked?

36 cm from one end

Which of these orbitals does not exist?

3f orbital.

A molecule of oxygen gas (O2 ) has a velocity of 2800 m / s. What is its de Broglie wavelength?

4.5 × 10−12 m

Determine the frequency of light required to move the electron of the Be3+ ion from the n = 1 to the n = 4 orbital. The atomic number of beryllium is 4.

4.94 × 1016 s−1

Determine the wavelength for electromagnetic radiation having a frequency of 5.55 × 1015 s−1.

5.40 × 10−8 m

Potassium (K) has a work function value of 2.29 eV. What is the wavelength of light required to begin to generate a current in an apparatus like the one Hertz used with potassium metal?

543 nm

The kinetic energy of a proton is 2.6 × 10−18 J. What is its de Broglie wavelength? (The mass of a proton is 1.67 × 10−27 kg.)

7.1 × 10−12 m

Determine the energy required to remove the electron from the 1s orbital of a Helium ion (He+ ).

8.72 × 10−18 J

Which of these particles will have the shortest de Broglie wavelength?

A proton with a velocity of 9.0 × 105 m / s

Which of the following metals requires ultraviolet light to exhibit the photoelectric effect?

Ag, work function = 4.74 eV

Which of the following diagrams is a plot of the 2p orbitals?

B - 3 infinity shaped orbitals on the Z,Y, and X axis

Which of the following statements about Einstein's explanation of the photoelectric effect is not correct?

Because light is packaged discretely, increasing the intensity of light will increase the number of photons hitting a metal and thus the likelihood that an electron will be ejected.

Which of the following represents the electron configuration for carbon?

C - 1s: full (2 e-) , 2s: full (2e-), 2p: 1 e- in 2 of the orbitals Explanation: This is the correct number of electrons and in the correct orientation. This diagram shows that the electrons in the 2p orbital are entering separate orbitals and have parallel spins.

Which of the following metals (with their associated threshold wavelength) has the lowest work-function value?

Cs, 602 nm

Which of the following is a correct statement of Hund's Rule?

Electrons will occupy separate degenerate orbitals and maintain parallel spins before pairing up.

Which of the following is not a consideration in the placement of electrons in an atom?

Heisenberg uncertainty principle

Where is / are the nodal plane(s) in this diagram of a d orbital.

In the x-y and x-z planes.

There are no known compounds of neon, a noble gas. Which of the following is the best explanation of the inert nature of neon?

It is both harder to add an electron to and remove an electron from neon, thus no compounds readily form.

Which of the following is the best explanation of why it is harder to remove an electron from an atom of neon than an atom of fluorine?

It is harder to remove an electron from neon than fluorine because of increased nuclear charge (Z = 10).

Choose the most correct statement about the kinetic energy of electrons ejected by a metal exhibiting the photoelectric effect.

It is the energy of the photon minus the work function for the metal.

What angular nodes does this picture of an f orbital display?

One nodal plane, two nodal cones.

Why doesn't Schrödinger's equation for the hydrogen atom work for the lithium atom?

Schrödinger's equation for the hydrogen atom only works for single electron species. It does not take into account the interaction between the electrons in multi-electron species.

What is the most significant conclusion to be drawn from the observations of the photoelectric effect?

That light is contained in discrete packages of energy.

What is the difference between a 2p and a 3p orbital.

The 3p orbital is farther from the nucleus than the 2p orbital.

What does the energy of the work-function value represent?

The amount of energy required to overcome the attractive forces between an electron and the bulk metal.

The work-function value for uranium metal is 3.63 eV. This energy is achieved with photons at a frequency of 8.77 × 1014 s−1 (near ultraviolet). If light of a lower frequency than this is applied, what will happen?

The current due to the photoelectric effect will disappear.

In which of the following ways does an electron in a hydrogen atom differ from a radio wave? (The mass of an electron is 9.11 × 10−31 kg.)

The electron will have a slower velocity.

How does the nuclear charge relate to the energy of the 1s orbital?

The energy of the orbital becomes more negative as the nuclear charge increases.

Though Neon is a relatively small atom with a relatively high nuclear charge, it is difficult to add an electron to a neon atom. Which of the following is the best explanation of this phenomenon?

The next electron added to neon would have to be placed in a higher energy level (the n = 3 level).

What is an orbital?

The probability of finding an electron in a region.

Which of the following statements correctly describes an observation of the photoelectric effect?

There is a frequency of light below which no electrons are emitted.

There are three p orbitals that are aligned with their major axes along the x, y, and z axes, what is the origin of these three p orbitals?

They are the solutions for the three values of the magnetic quantum number.

When is an electron said to have zero potential energy?

When it is infinitely separated from the nucleus.

With regard to the hydrogen atom, the difference in energy between the 3s orbital and the 4s orbital is _____________ the difference in energy between the 5s orbital and 6s orbital.

greater than

A beam of electrons is fired at a crystal of magnesium oxide, and photographic film is used to record the places where the electrons come through the crystal. Which of the following changes to the experiment is not likely to change the interference pattern that results on the film?

increasing the length of time the beam is fired at the crystal

Electrons in the 3s and 3p orbitals of hydrogen are at ___________ energy level(s), and electrons in the 2s and 3s orbitals of hydrogen are at ____________ energy level(s).

the same; different

Determine the energy of the electron in the 1s orbital of a helium ion (He+ ).

−8.72 × 10−18 J