Chapter 11: Atomic Phenomena

Question 1

At absolute zero (0 degrees Kelvin), what occurs:

Answer 1

all random atomic movement stops

Question 2

Blackbody radiators are:

Answer 2

ideal radiators with set light-radiation profiles, dependent on their temperature; ideal radiators are also ideal absorbers and appear black because they absorb all wavelengths of light (when at temperatures lower than their surroundings)

Question 3

The peak wavelength for a blackbody radiator is:

Answer 3

the wavelength at which the object radiates the greatest amount of energy; it is proportional to the blackbody’s absolute temperature

Question 4

The intensity of energy being radiated by a blackbody is proportional to:

Answer 4

the fourth power of the body’s absolute temperature

Question 5

Blackbody radiation is approximated by:

Answer 5

cavity radiation

Question 6

Equation to determine the peak wavelength emitted by an object at a given temperature (Wien’s Displacement Law):

Answer 6

(λ_peak)(T) = constant = 2.9 X 10^-3 m•K

Question 7

λ_peak refers to:

Answer 7

the wavelength at which more energy is emitted than at any other wavelength; it does not refer to the maximum wavelength emitted

Question 8

Equation to determine the total energy emitted by a blackbody (Stefan-Boltzmann Law):

Answer 8

E_T = σT⁴

where σ is a constant, T is the temperature, and E_T is the total energy emitted per unit of area

units = ^W/_m²

Question 9

The photoelectric effect is:

Answer 9

the ejection of an electron from the surface of a metal; it occurs in a vacuum when the metal is hit with incident light (a photon) that has a high enough energy to eject the electron

Question 10

The threshold frequency is:

Answer 10

the minimum light frequency necessary to eject an electron from a given metal; depends on the type of metal exposed to radiation

Question 11

Equation to determine the energy of a photon:

Answer 11

E = hf

where h is Planck’s constant and f is the frequency of the light. Once you know the frequency, you can find the wavelength using:

λ = ^c / _f

Question 12

The energy of a photon increases with:

Answer 12

increasing frequency

Question 13

Equation to determine the maximum kinetic energy of an electron ejected by an incident photon:

Answer 13

K_max = hf - W

where W is the work function of the metal in question

W = hf_t

Question 14

The Work Function is:

Answer 14

the minimum energy required to eject an electron and is related to the threshold frequency of a given metal:

W = hf_t

Question 15

Relationship between the frequency of the incident photon and the threshold frequency:

Answer 15

if the frequency of the incident photon is less than f_t, no electron will be ejected

if the frequency of the incident proton is greater than f_t, an electron will be ejected and the maximum kinetic energy will be the difference between hf and hf_t (the excess energy is converted into KE of the electron)

Question 16

If the photoelectric effect is occuring, what do electrons do?

Answer 16

electrons leaving the surface of the metal will form a current; the magnitude of this current is proportional to the intensity of the incident beam of photons

Question 17

The higher the principal quantum number, the higher the:

Answer 17

energy of an electron

Question 18

The Bohr Model of the Hydrogen Atom is:

Answer 18

an early quantum mechanical model of one-electron systems that proposes a hydrogen atom is a dense nucleus orbited by an electron

Question 19

For an electron to jump from a lower energy orbital to a higher energy orbital, it must:

Answer 19

absorb an amount of energy (hf) exactly equal to the difference between the two energy levels (in the form of a photon of light at the proper frequency)

Question 20

For an electron to jump from a higher energy orbital to a lower energy orbital, it must:

Answer 20

emit an amount of energy (hf) exaclty equal to the difference between the two energy levels (in the form of a photon of light at the proper frequency)

Question 21

Equation to estimate the energy of an electron with a given quantum number (n) in joules:

Answer 21

E = - ^Rh/_n²

where R is Rydberg’s constant and n is the quantum level

Question 22

Equation to estimate the energy of an electron with a given quantum number (n) in electron-volts (eV):

Answer 22

En = - ^{13.6 eV}/_n²

Question 23

The energy of an electron increases the farther is is from:

Answer 23

the nucleus; the energy gets less negative as it moves farther from the nucleus. Once the energy becomes positive, the electron is no longer bound to the nucleus

Question 24

In Bohr’s model, as n² increases, what happens to the energy of the electron?

Answer 24

it increases

Question 25

Ground state:

Answer 25

the small orbit an electron can be found; the lowest energy level; n = 1

Question 26

An excited state is:

Answer 26

any orbit higher than the electron’s ground state, and, thus, has more energy than the ground state

Question 27

Equation to determine the change in energy of an electron due to absorption or emission of a photon:

Answer 27

∆E = E_f - E_i

(both of these values will always be negative; if ∆E is negative, their was an emission of energy and the electron came down states)

units = joules

Question 28

Equation to determine the change in energy of an electron due to absorption or emission of a photon:

Answer 28

hf = |∆E|

units = joules

Question 29

Flourescence is a method by which:

Answer 29

absorbed high frequency light (usually UV) is emitted by a substance as lower frequency light (usually visible light); the electrons return to their ground state in multiple steps, releasing a lower-frequency photon than the absobed photon at each step

Question 30

Equation to find the wavelength of a photon:

Answer 30

λ = ^c/_f

where c = 3 X 10⁸