ch 9 - Atomic and Nuclear Phenomena

Question 1

photoelectric effect

Answer 1

when light of high frequency (blue to ultraviolet light) is incident on a metal in a vacuum, the metal atoms emit electrons; an “all or nothing” response

Question 2

current

Answer 2

created by electrons liberated from the metal by the photoelectric effect that produce a net charge flow per unit time

Question 3

threshold frequency (f sub T)

Answer 3

minimum frequency of light that causes ejection of electrons and depends on the type of metal being exposed to radiation

Question 4

f

Answer 4

if frequency of incident photon is less than the threshold frequency then no electron will be ejected because the photons do not have sufficient energy to dislodge the e- from its atom

Question 5

f>f sub T

Answer 5

If the frequency of incident photon is greater than the threshold frequency then an e- will be ejected and the maximum kinetic energy of the ejected e- will be equal to the difference between hf and hf sub T (also called the work function)

Question 6

energy of photon equation

Answer 6

E=hf; where E is energy of the photon of light, h is Planck’s constant (6.626 x 10^-34 Jxs); f = frequency of the light

Question 7

nanometer

Answer 7

1 nm = 10^-9 m

Question 8

angstroms

Answer 8

1 A = 10^-10 m

Question 9

max kinetic energy of the ejected e- equation

Answer 9

K sub max = hf - W; where h = Planck’s constant, f = frequency of the light, W = work function of the metal in question

Question 10

work function related to threshold frequency of a certain metal, equation

Answer 10

work function is the min energy required to eject an electron and is related to the threshold frequency by W = hf sub T; where W = work function of the metal in question; h = Planck’s constant; f sub T = threshold frequency

Question 11

infrared (IR) spectroscopy

Answer 11

used to determine chemical structure because different bonds will absorb different wavelengths of light

Question 12

UV-Vis spectroscopy

Answer 12

looks at the absorption of light in the visible and ultraviolet range

Question 13

note about indicators

Answer 13

most contain large organic compounds that have very different absorption patterns based solely on the protonation state of the compound. often have conjugated double bonds or aromatic ring systems which permit the absorption of light from photons in the visible range

Question 14

fluorescence

Answer 14

if a fluorescent substance is excited (such as a ruby, emerald or phosphors in fluorescent lights) with uv radiation, it will begin to glow with visible light; it is a stepwise photon emission in which an excited e- returns to the ground state through one or more intermediate excited states in which each step emits a photon

Question 15

mass defect

Answer 15

difference between the weight of the sum of protons and neutrons inside a nucleus and the actual weight of the nucleus which is slightly smaller

Question 16

equation embodying mass defect

Answer 16

E = mc^2; E = energy; m = mass and c = the speed of light; this is a result of matter that has been converted to energy

Question 17

strong nuclear force

Answer 17

force attaching protons and neutrons together to form the nucleus; strong enough to more than compensate for the repulsive electromagnetic force between the protons; acts over very short distances only

Question 18

binding energy

Answer 18

energy that is radiated away from the nucleus in the form of heat, light or other electromagnetic radiation before the mass defect becomes apparent; allows the nucleons to bind together in the nucleus

Question 19

weak nuclear force

Answer 19

also contributes to stability of the nucleus, but is one-millionth as strong as the strong nuclear force

Question 20

Four fundamental forces of nature

Answer 20

strong nuclear force, weak nuclear force, electrostatic forces and gravitation

Question 21

isotopic notation

Answer 21

notation in which elements are preceded by their atomic number as a subscript and mass number as a superscript

Question 22

atomic number (Z)

Answer 22

corresponds to number of protons in nucleus

Question 23

mass number (A)

Answer 23

corresponds to number of protons plus neutrons

Question 24

fusion

Answer 24

occurs when small nuclei combine to form a larger nucleus

Question 25

Fission

Answer 25

process by which a large nucleus splits into smaller nuclei; powers most nuclear power plants

Question 26

radioactive decay

Answer 26

naturally occurring spontaneous decay of certain nuclei accompanied by emission of specific particles

Question 27

Example of isotope decay arithmetic and nucleon conservation

Answer 27

X represents parent nucleus, Y represents daughter nucleus: (superscript A, subscript Z)X -> superscript A’, subscript Z’)Y + emitted decay particle; when balancing, sum of atomic numbers and mass numbers (separately) must be the same on both sides

Question 28

Alpha decay

Answer 28

emission of an alpha-particle which is a (superscript 4, subscript 2)He nucleus that consists of two protons, two neutrons, and zero electrons; carries double charge of beta-particle and is much bigger; interact with matter very easily and do not penetrate shielding very extensively

Question 29

balanced equation example of alpha decay

Answer 29

(superscript A, subscript Z)X -> (superscript A-4, subscript Z - 2)Y + (superscript 4, subscript 2)alpha

Question 30

Beta decay

Answer 30

emission of the beta-particle which is an electron and is given the symbol e- or beta-; electrons do not reside in nucleus but are emitted by the nucleus when a neutron decays into a proton, a beta-particle, and an antineutrino (v with a line over it); more penetrating and much smaller (electron is 1836 times smaller than proton) than alpha-particle

Question 31

positron emission

Answer 31

induced decay

Question 32

positron

Answer 32

has mass of an electron but is positively charged: symbol is e+ or beta+; a neutrino (v) is emitted in positron decay

Question 33

balanced equation example of beta- decay

Answer 33

(superscript A, subscript Z)X -> (superscript A, subscript Z + 1)Y + beta-; neutron is converted to electron so atomic number will be one more

Question 34

example equation of beta+ decay

Answer 34

proton is converted into a neutron and beta+ particle is emitted: (superscript A, subscript Z)X -> (superscript A, subscript Z-1)Y + beta+

Question 35

gamma decay

Answer 35

emission of gamma-rays which are high-energy (high-frequency) photons which carry no charge and simply lower the energy of the parent nucleus without changing the mass number or atomic number

Question 36

expression equation of gamma decay

Answer 36

(superscript A, subscript Z)X -> (superscript A, subscript Z)X + gamma

Question 37

electron capture

Answer 37

certain unstable radionuclides are capable of capturing an inner electron that combines with a proton to form a neutron, while releasing a neutrino. Atomic number is one less than the original but mass number remains the same; rare process best thought of as the reverse of beta- decay

Question 38

expression of electron capture

Answer 38

(superscript A, subscript Z)X + e- -> (superscript A, subscript Z-1)Y

Question 39

half-life (T sub 1/2)

Answer 39

in a sample of radioactive particles this is the time it takes for half of the sample to decay, in each subsequent half-life, one-half of the remaining sample decays so that the remaining amount asymptotically approaches zero

Question 40

exponential decay equation

Answer 40

delta n/delta t = -(sign for wavelength)n; sign for wavelength = known as decay constant; solution tells us how the number of radioactive nuclei changes with time

Question 41

exponential decay equation

Answer 41

n = n sub 0 x e (to the power of -wavelength sign (decay constant) x t); n sub 0 = number of undecayed nuclei at time t = 0

Question 42

decay constant is related to the half-life by this equation

Answer 42

decay constant (upside down y) = (ln2)/(T sub 1/2) = (0.693)/(T sub 1/2)