Nuclear Phenomena

Question 1

Atomic Number (Z)

Answer 1

The number of protons in the nucleus

Question 2

Mass Number (A)

Answer 2

A = N + Z

Question 3

Isotope

Answer 3

Same element, different numbers of neutrons

Question 4

Atomic Mass Unit

Answer 4

1 amu = 1/12 mass of neutral Carbon-12 atom = 1.66 X 10^-27 kg = 1.66 X 10^-24 g

Question 5

Nuclear Binding Energy

Answer 5

Energy that holds nucleus together defined by E = mc^2

Question 6

Mass Defect

Answer 6

Difference between atom’s atomic mass and sum of masses of its protons and neutrons.

Question 7

Fusion

Answer 7

Two or more smaller nuclei combine to form larger nucleus

Question 8

Fission

Answer 8

Large nucleus splits into smaller nuclei

Question 9

Why do nuclear fusion and nuclear fission release energy?

Answer 9

initial mass > final mass

Question 10

Alpha Decay

Answer 10

Emission of alpha particle (a Helium atom)

Subtract two protons and two neutrons

Question 11

Beta Decay

Answer 11

Emission of a beta particle (an electron)

Add a proton when electron emitted, subtract one when positron emitted

Question 12

Gamma Decay

Answer 12

Emission of high energy photons, does not change mass or proton number

Question 13

Electron Capture

Answer 13

Nucleus captures inner-shell electron leading to neutron formation, so atomic number decreases by 1, but atomic mass remains the same

Question 14

Half-Life

Answer 14

T(1/2) = ln 2/λ

Fraction of original nuclei remaining after n half-lives is (1/2)^n

Question 15

Exponential Decay

Answer 15

-λn = Δn/ Δt
Number of nuclei that decayed in time t = n(0) - n
n = n(0)e^-λt