Chapter 7 Test

Question 1

Under what circumstances does the Bohr model fail to make accurate predictions of an atom’s spectra?

Answer 1

When the number of electrons in the atom is greater than 1

Question 2

What is the energy per photon of the lowest frequency of electromagnetic radiation that can be used to observe a gold atom with a diameter of 280 picometers? (1 picometer = 1 × 10−12 meter)

Answer 2

7.1 × 10^−16 J

Question 3

Which of the following would provide the greatest resolution in order to observe a virus?

Answer 3

electromagnetic radiation with a frequency of 7.3 × 10^18 s−1

Question 4

Why are X-rays, rather than visible light, used in airport security systems that scan luggage?

Answer 4

X-rays can penetrate the outside of the suitcase to “see” what is inside.

Question 5

An atom of helium
has a de Broglie wavelength of
4.3 × 10^−12 meters.

What is its velocity?

Answer 5

2.3 × 10^4 m / s

Question 6

Which of the following graphs best represents the probability of finding an electron in any direction of a 2s orbital?

Answer 6

In a 2s orbital, the probability of finding an electron is relatively high close to the nucleus. This region of high probability is followed by a radial node, where the probability of finding the electron is zero. The node is then followed by a second region of fairly high probability. This graph correctly shows two regions of high probability with a radial node in between them.

Question 7

The x-, y-, and z-coordinates of a point are (1, 0, 0). What are the values of θ and φ for this point, using spherical coordinates? (Assume that θ is the angle between the point and the z-axis and that φ is the angle between the x-axis and a projection of the point onto the xy-plane.)

Answer 7

θ = 90°; φ = 0°

Question 8

A point has spherical coordinates (r, θ, φ) of (5, 90°, 90°). What are the rectangular coordinates (x, y, z) of this point? (Assume that θ is the angle between the point and the z-axis and that φ is the angle between the x-axis and a projection of the point onto the xy-plane.)

Answer 8

(0, 5, 0)

Question 9

What would a 2py orbital look like if the angular part of its wave function were constant?

Answer 9

Its shape would be similar to that of a 1s orbital.

Question 10

How many unique distinct values of ml 3d orbitals are there and how many angular nodes does each 3d orbital have?

Answer 10

5 and 2

Question 11

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

Answer 11

One nodal plane, two nodal cones.

Question 12

Which of the following cannot absorb a visible photon?

Answer 12

He2+

Question 13

Determine the wavelength for electromagnetic radiation having a frequency of 5.55 × 10^15 s−1

Answer 13

5.40 × 10^−8 m

Question 14

When is an electron said to have zero potential energy?

Answer 14

When it is infinitely separated from the nucleus.

Question 15

What is the name for the “1” in “1s orbital” or the “2” in “2p orbital”?

Answer 15

principal quantum number

Question 16

Which of these correctly describes the relationship between ultraviolet light and visible light?

Answer 16

Ultraviolet light is electromagnetic radiation of higher frequencies and shorter wavelengths than visible light.

Question 17

In which of the following ways do electromagnetic waves (moving through a vacuum) differ from water waves (moving across an ocean)?

Answer 17

Unlike that of electromagnetic waves, the speed of water waves may vary.

Question 18

Suppose you are in a room in which the only light source emits wavelengths of green light and no other colors. What color will an apple that appears red in white light will appear in this room?

Answer 18

black

Question 19

In order for a cat to become invisible, its body would have to __________ all wavelengths of visible light.

Answer 19

transmit

Question 20

What process at the atomic level is responsible for the production of incandescent light from a hot metal?

Answer 20

Vibrating nuclei within the atom create electromagnetic radiation.

Question 21

An object is heated to a high temperature and emits light. The overall color of the object appears orange. Which of the following is true about the frequencies of light emitted by the object?

Answer 21

The object emits frequencies of light in the ultraviolet, visible, and infrared regions of the spectrum.

Question 22

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

Answer 22

That light is contained in discrete packages of energy.

Question 23

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

Answer 23

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

Question 24

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?

Answer 24

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

Question 25

Which of the following explains why the Bohr model of the atom ultimately did not work?

Answer 25

It required knowing the position and momentum of an electron