Glencoe Review Ch. 4
1. Explain why all atoms are electrically neutral.
# of protons = # electrons
2. Are the following isotopes of each other? 24Mg, 25Mg, 26Mg Explain.
Yes – same element but different # of neutrons
3. An isotope of mercury has 124 neutrons. What is its mass number?
204
4. When looking at information on the 19F atom, you see this number: 18.9984. Give the unit that probably
follows this value.
amu
5. How many protons, electrons and neutrons are contained in an atom of 70Zn?
30 p 30 e 40n
6. Give the nuclear symbol for cobalt containing 28 neutrons and 25 electrons.
7. Silver has two stable isotopes: 107Ag which has a mass of 106.905 amu and 109Ag which has a mass of
108.905amu. What is the mass percent of each isotope?
51.8500% of 107 Ag and 48.1500% of 109Ag
8. An element has four naturally occurring isotopes. At 4.35% abundance is an isotope with a mass of 49.946
amu. The isotope with a mass percent of 83.79% has a mass of 51.941 amu. A third isotope occurs 9.50% of
the time and has a mass of 52.941 amu. The fourth isotope has a mass of 53.939 amu. What is the average
atomic mass of this element?
52.0 amu
9. Calculate the mass in grams of 7.98 x 1018 oxygen atoms.
0.000212 grams
10. How many atoms will be in 1.25 grams of chlorine atoms?
2.12 x 1022 atoms
11. What is the change in atomic number when these particles are emitted?
a) alpha particle
b) positron
c) electron
a) down by 2
b) down by 1
c) up by 1
d) no change
12. Write nuclear reactions for these:
a) 10B emitting α particles

b)
c) turning 230Ac into 230Th

d) β+ decay of

137
Cs capturing an electron
+

d) gamma radiation
13. Burning gasoline releases 47.8 kJ/g. One atom of uranium releases 2.79 x 10-11 J of energy. How much
energy would be released by one gram of uranium? Bonus: How much more energy is this than the energy
released by one gram of gasoline?
7 x 1010 J
Bonus: 1,000,000 times more energy
14. Write the most likely nuclear reaction for 18O. Hint: Does this oxygen atom appear to have too many or
too few neutrons? Which process would help fix this imbalance (β+, β- or electron capture)?
Beta minus decay since this turns a neutron into a proton. 18O has more neutrons than protons and will likely
try to create another proton instead of making another extra neutron.
15. Complete the following equations and identify the type of nuclear reaction occurring:
a) 9Be + 2H 
fusion
c)
fission
b) _
d)
_

electron capture
beta plus decay
16. Which of the above reactions could be involved in a chain reaction? Tell how you know.
c) because neutrons are produced
17. Which of the reactions in question 15 might occur in a star? What makes you think so?
a) fission occurs in stars
18. What two precautions do the designers of nuclear power plants take to ensure that the uranium in the plant
cannot detonate like a nuclear bomb?
1. power plants do not contain the critical mass of uranium
2. the uranium in power plants does not have the required shape
19. Give two benefits and one drawback of obtaining electricity from a nuclear fusion power plant.
B: reduced dependence on nonrenewable resources and less air pollution
D: no clear method for dealing with radioactive waste and potential for accidents
20. Which of these isotopes is more likely to decay by β– decay: 18N or 12N? Explain how you know.
18
N because it has far more neutrons than protons and beta minus decay turns neutrons into protons.
Bonus: 1H + 2H  3He + γ is one of the reactions in the Sun. The mass of 1H is 1.007825 amu, the mass of
2
H is 2.014102 amu and the mass of 3He is 3.016029 amu. What energy is released when one atom of 3He is
formed?
8.803 x 10-13 Joules