7. Atomic and Nuclear Physics

Question 1

Photon

Answer 1

a discrete unit or package of light energy

Question 2

Nuclide

Answer 2

a particular type of nucleus with a certain number of protons and neutrons

Question 3

Isotope

Answer 3

nuclei with the same number of protons (Z) but different number of neutrons (N)

Question 4

Nucleon

Answer 4

a proton or neutron

Question 5

Nucleon Number (Mass Number) (A)

Answer 5

number of nucleons

Question 6

Proton Number (Atomic Number) (Z)

Answer 6

number of protons in nucleus

Question 7

Neutron Number (N)

Answer 7

number of neutrons in nucleus (N = A – Z)

Question 8

Coulomb interaction (Coulomb force, electrostatic force)

Answer 8

electrostatic force of repulsion between the protons in the nucleus

Question 9

Radioactive Decay

Answer 9

when an unstable nucleus emits a particle (alpha, beta, gamma)

• random
• spontaneous

Question 10

Alpha Particle (α)

Answer 10

helium nucleus (2 protons + 2 neutrons)

Question 11

Beta Positive Particle (β+)

Answer 11

electron

Question 12

Beta Negative Particle (β-)

Answer 12

positron (antielectron)

Question 13

Gamma Radiation (γ)

Answer 13

high energy (high frequency) electromagnetic radiation

Question 14

Radioactive Half-life (T1/2)

Answer 14

a. the time taken for ½ the number of radioactive nuclei in sample to decay
b. the time taken for the activity of a sample to decrease to ½ its initial value

Question 15

Artificial (Induced) Transmutation

Answer 15

when a nucleus is bombarded with a nucleon, an alpha particle or another small nucleus, resulting in a nuclide with a different proton number (a different element)

Question 16

Unified Atomic Mass Unit

Answer 16

1/12th the mass of a carbon-12 nucleus

Question 17

Mass Defect

Answer 17

difference between the mass of the nucleus and the sum of the masses of its individual nucleons

Question 18

Binding Energy

Answer 18

energy released when a nuclide is assembled from its individual components (OR: energy required when nucleus is separated into its individual components)

Question 19

Binding Energy per Nucleon

Answer 19

energy released per nucleon when a nuclide is assembled from its individual components

Question 20

Nuclear Fission

Answer 20

a heavy nucleus splits into two smaller nuclei of roughly equal mass

Question 21

Nuclear Fusion

Answer 21

two light nuclei join to form a heavier - source of the suns energy

Question 22

Photoelectric Effect

Answer 22

the emission of electrons from a metal when electromagnetic radiation of high enough frequency falls on the surface

Question 23

Threshold Frequency (f0)

Answer 23

minimum frequency of light needed to eject electrons from a metal surface

Question 24

Work Function (Φ)

Answer 24

minimum energy needed to eject electrons from the surface of a metal

Question 25

Millikan’s Stopping Potential Experiment

Answer 25

an experiment utilizing reverse voltage raised to such a level (stopping potential Vs) that it stops all emitted photoelectrons

Question 26

de Broglie Hypothesis

Answer 26

All particles can behave like waves whose wavelength is given by λ = h/p where h is Planck’s constant and p is the momentum of the particle.

Question 27

Matter Waves

Answer 27

All moving particles have a “matter wave” associated with them whose wavelength is the de Broglie wavelength.

Question 28

Wave-Particle Duality

Answer 28

Both matter and radiation have a dual nature. They exhibit both particle and wave properties.

Question 29

172. Bainbridge Mass Spectrometer

Answer 29

a device used to determine atomic masses – consists primarily of a velocity selector and a magnetic chamber

Question 30

Radioactive Decay Law

Answer 30

The rate at which radioactive nuclei in a sample decay (the activity) is proportional to the number of radioactive nuclei present in the sample at any one time. (A = λN)

Question 31

Decay Constant (λ)

Answer 31

a. constant of proportionality between the decay rate (activity) and the number of radioactive nuclei present
b. probability of decay of a particular nuclei per unit time

Question 32

Activity (A)

Answer 32

number of radioactive disintegrations (decays) per unit time