Section 8 - Stable nuclei
8.1 Lead is an element that has 82 protons in its nucleus. Which of the following mass numbers is most likely to correspond to a
stable isotope of lead?
i. 41
ii. 123
iii. 164
iv. 206
v. 246
Section 9 - Nuclear binding energy
9.1 What is the binding energy for a nucleus of helium-4, also known as an alpha particle? A neutron has a mass of 1.00866 u, a
proton has a mass of 1.00728 u, and an alpha particle has a mass of 4.00153 u, where u = 1.66054×10í^27 kg. Express the
energy in joules to three significant figures.
J
Section 13 - Fission
13.1 Consider the fission reaction that occurs when a neutron is captured by a uranium-235 atom and fissions into xenon-140,
strontium-94, and 2 neutrons. Calculate the energy released in this reaction. The masses are: neutron = 1.0087 u, uranium-
235 = 235.0439 u, xenon-140 = 139.9216 u, strontium-94 = 93.9154 u.
J
Section 14 - Fusion
14.1 In the sun, 4 hydrogen nuclei undergo a multi-step process and eventually form a helium-4 nucleus (plus some positrons,
neutrinos and gamma rays, all of negligible mass). For each helium atom produced, about 26 MeV of energy is released. (a)
Which has more mass, the 4 hydrogen atoms or the helium-4 atom? (b) What is the magnitude of the mass difference?
(a) 4 hydrogen atoms 1 helium-4 atom
(b) kg
14.2 The sun radiates electromagnetic energy at the rate of 3.91×10^26 W. (a) What is the change in the sun's mass during one
second? Express the answer as a positive mass. (b) The current mass of the sun is 1.99×10^30 kg. What fraction of the sun's
mass is lost in a century? Express the answer as a decimal number and assume years of 365.25 days.
(a) kg
(b)
Section 15 - Radioactivity and radiation
15.1 An excited nucleus emits a gamma ray of energy 7.5 MeV. (a) Does the nuclear mass increase, or does it decrease? (b)
What is the magnitude of the change?
(a) Increase Decrease
(b) kg
15.2 A carbon-14 atom decays into nitrogen-14 (Z = 7). What particle(s) did it emit?
i. Positive beta
ii. Negative beta
iii. Gamma
iv. Two alphaparticle(s)15.3 A uranium-238 nucleus decays into a uranium-234 nucleus. What particle(s) did it emit?
i. Four positive beta
ii. One alpha
iii. Two alpha and two negative beta
iv. One alpha and two negative betaparticle(s)