Conceptual Questions:
1. List the conservation laws relating to nuclear reactions.
2. The atomic number of a given element is equivalent to which of the following?
a. proton number in the nucleus
b. neutron number in the nucleus
c. sum of the protons and neutrons in the nucleus
d. number of electrons in the outer shells
3. The ratio of the numbers of neutrons to protons in the nucleus of naturally occurring isotopes tends to vary with atomic number in what manner?
a. increases with greater atomic number
b. decreases with greater atomic number
c. is maximum for atomic number = 60
d. remains constant for entire range of atomic numbers
Numerical Problems: help is here.
1. Radium-226 (Z=88) decays to Radon-222 (Z=86) by emitting which of the following?
a. beta
b. alpha
c. gamma
d. positron
2. If a fossil bone is found to contain 1/8th as much Carbon-14 as the bone of a living animal, what is the approximate age of the fossil? (half-life of C-14 = 5800 years)
ans: 17,400 years
the bone loses 1/2 C-14 in 5800 years, 1/2 of remaining in next
5800 years, 1/2 of that remaining in next 5800 years, leaving 1/8.
3. Chromium-55 (54.9279 u) emits an electron (0.0005 u) leaving a daughter nucleus of manganese-55 (54.9244 u). How much energy is released in this reaction? (1 u x c2 = 931 MeV)
ans: 2.79 MeV
E = m*c*c
4. The beta emission process results in the daughter nucleus differing in what manner from the parent?
a. atomic mass increases by one
b. atomic number decreases by two
c. atomic number increases by one
d. atomic mass decreases by two
5. A radioactive isotope that emits a gamma quantum will change in what respect?
a. atomic number increases by one
b. atomic number decreases by one
c. atomic mass number decreases by one
d. none of the above choices are valid
6. What is the binding energy per nucleon of Au-197 (atomic number = 79)? (The following information regarding atomic masses will be needed: Au-197, 196.966560; proton, 1.007825; neutron, 1.008665; also 1 u x c2 = 931.5 MeV)
ans: 7.9 MeV
add up all the proton, neutron masses to get total mass of loose
particles- subtract mass of combined Au (gold) to get total binding
energy (in mass units)- then divide by number of particles to get
binding energy-mass per particle.
7. An oxygen-16 atom captures a proton and in turn emits a deuteron. What is the element and mass number of the product isotope?
a. nitrogen-15
b. oxygen-17
c. oxygen-15
d. fluorine-15
8. The neutron is radioactive and can beta decay to form a proton. This can occur primarily because:
a. the proton has less mass than a neutron.
b. there are several hydrogen isotopes.
c. of the binding energy of hydrogen.
d. the neutron is neutral.
9. Certain stars at the end of their lives are thought to collapse combining their protons and electrons together to form a neutron star. Such a star could be thought of as a giant atomic nucleus. If a star of mass equal to that of the sun (M = 2 x1030 kg) collapsed into neutrons (mn = 1.67 x10-27 kg), what would be the radius of such a star? [HINT: r = r0*A1/3]
ans: 12.7 km
see HINT.