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ATOMIC THEORY
HISTORY OF THE ATOM
The original idea (400 B.C.) came from ______________________, a Greek philosopher.
He expressed the belief that all matter is composed of very small, indivisible particles, which he named
atomos. John Dalton (1766-1844), an English school teacher and chemist, proposed his atomic theory
of matter in 1803. Dalton’s Atomic Theory states that:
1. All matter is made of tiny __________________________ particles called atoms.
2. Atoms of the ____________ element are identical; those of different atoms are different.
3. Atoms of different elements combine in whole number ________________ to form compounds
4. Chemical reactions involve the rearrangement of atoms. No _______ atoms are created or destroyed.
PARTS OF THE ATOM
Because of Dalton’s atomic theory, most scientists in the 1800s believed that the atom was like a tiny
solid ball that could not be broken up into parts. In 1897, a British physicist, J.J. Thomson, discovered
that this solid-ball model was not accurate. Thomson’s experiments used a __________________ ray
tube. It is a vacuum tube - all the air has been pumped out. Because these rays originate at the
____________________, they are called cathode rays. Thomson concluded that cathode rays are
made up of invisible, _________________________ charged particles referred to as electrons. From
Thomson’s experiments, scientists had to conclude that atoms were not just neutral
_________________, but somehow were composed of electrically charged particles. Matter is not
negatively charged, so atoms can’t be negatively charged either. If atoms contained extremely light,
negatively charged particles, then they must also contain positively charged particles — probably with
a much greater _____________ than electrons. J.J. Thomson said the atom was like ______________
pudding, a popular English dessert.
In 1909, a team of scientists led by Ernest Rutherford in England carried out the first of several
important experiments that revealed an arrangement far different from the plum pudding model of the
atom. The experimenters set up a lead-shielded box containing radioactive polonium, which emitted a
beam of positively charged subatomic particles through a small hole. The sheet of ________________
foil was surrounded by a screen coated with zinc sulfide, which glows when struck by the positively
charged particles of the beam. The ________________ particles were expected to pass through
without changing direction very much because Rutherford thought the mass was evenly distributed in
the atom. Because most of the particles passed through the foil, they concluded that the atom is nearly
all _______________ ______________. Because so few particles were deflected, they proposed that
the atom has a small, dense, positively charged central core, called a ____________________. Alpha
particles are deflected by it if they get close enough to the nucleus.
R.A. Millikan found the charge of an electron to be -1.60 x 10-19 Coulombs in his famous oil
drop experiment. In 1910, J.J. Thomson discovered that neon consisted of atoms of two different
masses. Atoms of an element that are chemically alike but differ in mass are called
______________________ of the element. Because of the discovery of isotopes, scientists
hypothesized that atoms contained still a third type of particle that explained these differences in mass.
Calculations showed that such a particle should have a mass ____________________ to that of a
proton but no electrical _______________. The existence of this neutral particle, called a neutron, was
confirmed in the early 1930s. James _________________ is given credit for discovering the neutron.
NAME
SYMBOL
CHARGE
RELATIVE MASS
1/2000
proton
no
MODERN VIEW OF THE ATOM
The atom has two regions and is ___-dimensional. The nucleus is at the ___________________ and
contains the protons and _____________________. The electron cloud is the region where you might
find an electron and most of the volume of an atom. The atomic _________________ of an element is
the number of protons in the nucleus of an atom of that element. The number of protons determines
____________________ of an element, as well as many of its chemical and physical properties.
Because atoms have no overall electrical charge, an atom must have as many ____________________
as there are protons in its nucleus. Therefore, the atomic number of an element also tells the number of
electrons in a neutral atom of that element. The mass of a neutron is almost the same as the mass of a
________________. The sum of the protons and neutrons in the nucleus is the ________________
number of that particular atom. _____________________ of an element have different mass numbers
because they have different numbers of _______________, but they all have the same atomic number.
AVERAGE ATOMIC MASS
The atomic mass is the weighted average mass of all the naturally occurring isotopes of that element.
To determine the average atomic mass, first calculate the contribution of each isotope to the average
atomic mass, being sure to convert each ___ a fractional abundance. The average atomic mass of the
element is the sum of the mass contributions of each isotope.
Elements can be represented by using the symbol of the element, the mass number and the atomic
number. The mass number is the __________________ mass rounded to a whole number.
1. Determine the following for the fluorine-19 atom.
a) number of protons
b) number of neutrons
d) atomic number
e) mass number
c) number of electrons
2. Repeat #1 for bromine-80.
3. If an element has an atomic number of 34 and a mass number of 78, what is the
a) number of protons
b) number of neutrons
c) number of electrons
d) complete symbol
4. If an element has 91 protons and 140 neutrons, what is the
a) atomic number
b) mass number
c) number of electrons
d) complete symbol
5. If an element has 78 electrons and 117 neutrons what is the
a) atomic number
b) mass number
c) number of protons
d) complete symbol
Practice/Homework
Isotopes and Subatomic Particles
Complete the chart
Isotope symbol
207
82
Atomic #
Mass
Protons
Neutrons
Electrons
8
9
77
54
Pb
38
12
50
13
106
11
7
157
12
14
11
126
85
238
92
U
75
33
As
32
16
65
29
S
Cu
202
80
Hg
47
40
24
261
104
Rf
61
51
28
MOLES
We measure ________________ in grams. We measure volume in __________________. We count
pieces in _________________. The number of moles is defined as the number of
__________________ atoms in exactly ____ grams of carbon-12. ____ mole is 6.022 x 1023 particles.
6.022 x 1023 is called __________________ number. Representative particles are the smallest pieces
of a substance. For a molecular compound it is a(n) ______________________. For an ionic
compound it is a ______________________ ______________. For an element it is a(n)
________________.
How many oxygen atoms are in the following?
a) CaCO3
b) Al2(SO4)3
How many total ions are in the following?
a) CaCl2
b) NaF
c) Al2S3
Representative
particles
Volume
Use
22.4
L
Use
6.02x1023
moles
Use
molar mass
mass
Remember DIMO:
Divide
In
Multiply
Out
MOLE CONVERSIONS
1. How many atoms of carbon are there in 1.23 moles of carbon?
2. How many molecules of CO2 are in 4.56 moles of CO2?
3. How many atoms of iron are in 0.600 moles of iron?
4. How many moles are in 7.78 x 1024 formula units of MgCl2?
5. How many moles of water are 5.87 x 1022 molecules of water?
6. How many moles of aluminum are 1.2 x 1024 atoms of aluminum?
Calculate the number of particles (atoms, ions or molecules) in each of the following.
a) 3.4 moles Na2S
b) 0.0020 moles Zn
c) 1.77 x 10-11 moles C
d) 92.35 moles O2
Calculate the number of moles in each of the following.
a) 3.4 x 1024 molecules HCl
b) 8.7 x 1021 atoms Zn
c) 1.77 x 1018 ions Al+3
d) 2.66 x 1026 atoms Cu
MOLAR MASS
Molar mass is the generic term for the mass of one _____________. It may also be referred to as gram
molecular mass, gram formula mass, and gram atomic mass. The unit is ______________. To
determine the molar mass of an element, find the element’s symbol on the periodic table and round the
mass so there is __________ digit beyond the decimal.
Determine the molar mass of the each of the following elements.
a) sulfur (S)
b) chromium (Cr)
c) bromine (Br)
To determine the molar mass of a compound, find the mass of all elements in the compound.
If necessary, ___________________ an element’s mass by the subscript appearing beside that element
in the compound’s formula (or ________________ of the subscripts).
Calculate the molar mass of each of the following compounds.
a) Na2S
b) N2O4
c) C6H12O6
d) Ca(NO3)2
MASS-PARTICLE/MOLE CONVERSIONS
1. How many atoms of lithium are in 1.00 g of Li?
2. How many molecules of sodium oxide are in 42.0 g of Na2O?
3. How much would 3.45 x 1022 atoms of uranium (U) weigh?
4. How many moles of magnesium are in 56.3 g of Mg?
5. How many moles is 5.69 g of NaOH?
6. How many grams of sodium chloride are in 3.45 moles of NaCl?
7. How many moles is 4.8 g of CO2?
8. How many grams is 9.87 moles of H2O?
9. How many molecules are in 6.8 g of CH4?
10. What is the mass of 49.0 molecules of C6H12O6?
GASES
Many of the chemicals we deal with are gases. They are difficult to weigh, and we need to know how
many moles of gas we have. Two things affect the volume of a gas: temperature and pressure.
Standard temperature is ______ ºC, and standard pressure is ______ atm. Standard temperature and
pressure is abbreviated STP. At STP 1 mole of gas occupies ______ L. 22.4 L is called the
_____________ volume. Avogadro’s Hypothesis - At the same temperature and pressure equal
volumes of gas have the same number of _______________________.
GAS CONVERSIONS
1. What is the volume of 4.59 mole of CO2 gas at STP?
2. How many moles is 5.67 L of O2 at STP?
3. What is the volume of 8.8 g of CH4 gas at STP?
4. How many grams is 16.2 L of O2 at STP?
Calculate the number of liters in each of the following.
a) 3.10 x 1024 molecules Cl2
b) 8.7 moles Ne
c) 2.77 x 1018 atoms He
d) 266 grams SO2
Homework/Practice
Part 1--Convert between particles and moles
1. 24 atoms of sodium = _____ moles of sodium atoms
2. 5 molecules of chlorine gas = _____ moles of chlorine molecules
3. 900 atoms of silver
= _____ moles of silver atoms
4. 2.89 x 1023 molecules of ammonia = _____ moles of ammonia molecules
5. 15 moles of arsenic atoms = ______ atoms of arsenic
6. 4.00 x 103 moles of barium atoms = __________ atoms of barium
Part 2--Convert between mass and moles
7. Calculate the mass of 1.000 mole of CaCl2
8. Calculate grams in 3.0000 moles of CO2
9. Calculate number of moles in 32.0 g of CH4
10. Calculate moles in 168.0 g of HgS
11. Calculate moles in 510.0 g of Al2S3
12. How many moles are in 27.00 g of H2O
13. What is the mass of 2.55 moles Cu2CrO4
Part 3- Multiple steps
14. Arrange the following in order of increasing weight.
a. 10.4 g of sulfur
c. 6.33 x 1025 atoms of hydrogen
b. 0.179 moles of iron
d. 0.77 moles of N2
15. How many grams would 8.1  1021 molecules of sucrose (C12H22O11) weigh?
16. How many atoms are in a 2.0 kg ingot of gold? (Note mass units.)
17. What is the mass of 2.3x1024 molecules of KCl?
18. Calculate the number of molecules in 50.0 grams of H2SO4
19. Calculate the number of molecules in 100. grams of KClO4
20. Calculate the number of molecules in 8.76 grams of NaOH
21. Calculate the mass of 1.2x1022 molecules of Fe3(PO4)2
22. Calculate mass of 7.2x1024 molecules of Na2CO3
NUCLEAR CHEMISTRY
Nuclear chemistry is the study of the structure of _________________ nuclei and the changes they
undergo. Marie Curie named the process by which materials such as uranium give off rays
radioactivity; the rays and particles emitted by a radioactive source are called __________________.
As you may recall, isotopes are atoms of the same element that have different numbers of
_________________. Isotopes of atoms with unstable nuclei are called ______________________.
These unstable nuclei emit radiation to attain more stable atomic configurations in a process called
radioactive ________________. During radioactive decay, unstable atoms lose _________________
by emitting one of several types of radiation.
TYPES OF RADIATION
The three most common types of radiation are alpha (α), ____________ (β), and gamma (γ). An alpha
particle (α) has the same composition as a __________________ nucleus - two protons and ________
neutrons - and is therefore given the symbol _________. The charge of an alpha particle is 2+ due to
the presence of the two ___________________. Because of their mass and charge, alpha particles are
relatively slow-moving compared with other types of radiation. Thus, alpha particles are not very
________________________ - a single sheet of paper stops alpha particles. A beta particle is a veryfast moving ______________________ that has been emitted from a neutron of an unstable nucleus.
Beta particles are represented by the symbol _________. The zero superscript indicates the
insignificant mass of an electron in comparison with the mass of a ____________________. The –1
subscript denotes the _____________________ charge of the particle. Beta radiation consists of a
stream of fast-moving electrons. Because beta particles are both lightweight and fast moving, they
have _____________________ penetrating power than alpha particles. A thin metal foil is required to
stop beta particles. Gamma rays are high-energy (_________________ wavelength) electromagnetic
radiation. They are denoted by the symbol __________. As you can see from the symbol, both the
subscript and superscript are zero. Thus, the emission of gamma rays does not change the
__________________ number or mass number of a nucleus. Gamma rays almost always accompany
alpha and beta radiation, as they account for most of the energy loss that occurs as a nucleus decays.
NAME
SYMBOL
alpha
FORMULA
4
2
MASS
CHARGE
DESCRIPTION
He
β
-1
0
High energy
radiation
NUCLEAR STABILITY and DECAY
Radioactive nuclei undergo decay in order to gain _____________________. All elements with
atomic numbers greater than 83 are radioactive. Nuclear equations are used to show nuclear
transformations. Balanced nuclear equations require that both the ____________________ number
and the mass number must be balanced.

When beryllium-9 is bombarded with alpha particles (helium nuclei), a neutron is produced. The
balanced nuclear reaction is given as: ________________________________________________
The atomic number (the number on the bottom) determines the identity of the element.

When nitrogen-14 is bombarded with a neutron, a proton is produced. The balanced nuclear
equation can be written as: _________________________________________________________

Polonium-230 undergoes alpha decay: ________________________________________________

Uranium-234 undergoes alpha decay: ________________________________________________

Cobalt-50 undergoes beta decay: ____________________________________________________
Provide symbols for each of the following: neutron ___________, proton ___________ or
___________, and the positron ___________.

What element is formed when iron-60 undergoes beta decay? Give the atomic number and mass
number of the element. ____________

Write a balanced nuclear equation for the alpha decay of the following radioisotope, uranium-235.
____________________________________________________________

Nitrogen-12 decays into a positron and another element. Write the balanced nuclear equation.
____________________________________________________________

Uranium-238 is bombarded with a neutron. One product forms along with gamma radiation.
Write the balanced nuclear equation.
____________________________________________________________

Nitrogen-14 is bombarded with deuterium (hydrogen-2). One product forms along with an alpha
particle. Write the balanced nuclear equation.
____________________________________________________________
RADIOACTIVE DECAY RATES
Radioactive decay rates are measured in half-lives. A half-life is the time required for one-half of a
radioisotope’s nuclei to ________________ into its products. For example, the half-life of the
radioisotope strontium-90 is 29 years. If you had 10.0 g of strontium-90 today, 29 years from now you
would have 5.0 g left. The decay continues until negligible strontium-90 remains.

Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is
44.5 days. How much of a 2.000-mg sample will remain after 133.5 days? ______________

Cobalt-60 has a half-life of 5.27 years. How much of a 10.0 g sample will remain after
21.08 years?

Carbon-14 has a half-life of 5730 years. How much of a 250. g sample will remain after
5730 years?
FISSION and FUSION
Heavy atoms (mass number > 60) tend to break into smaller atoms, thereby increasing their
________________________. Using a neutron to split a nucleus into fragments is called nuclear
_______________________. Nuclear fission releases a large amount of energy and several neutrons.
Since neutrons are products, one fission reaction can lead to more fission reactions, a process called a
________________ reaction. A chain reaction can occur only if the starting material has enough mass
to sustain a chain reaction; this amount is called _______________________ mass. The
_____________________ of atomic nuclei is called nuclear fusion. For example, nuclear fusion
occurs within the Sun, where hydrogen atoms fuse to form ____________________ atoms. Fusion
reactions can release very large amounts of energy but require extremely high temperatures. For this
reason, they are also called _____________________________ reactions.
APPLICATIONS OF NUCLEAR REACTIONS
Geiger counters, scintillation counters, and film badges are devices used to detect and measure
radiation. Geiger counters use ________________________ radiation, which produces an electric
current in the counter, to rate the strength of the radiation on a scale. Film badges are often used to
monitor the approximate radiation ______________________ of people working with radioactive
materials. Scintillation counters measure ionizing radiation. With proper safety procedures, radiation
can be useful in industry, in scientific experiments, and in medical procedures. Nuclear power plants
use the process of nuclear fission to produce heat in nuclear reactors. The heat is used to generate
steam, which is then used to drive __________________ that produce electricity. A radiotracer is a
radioisotope that emits non-ionizing radiation and is used to signal the presence of an element or of a
specific substance. Radiotracers are used to detect ______________________ and to analyze complex
chemical reactions. Ionizing radiation has many uses. A(n) _______________ is ionizing radiation,
and ionizing radiation can be used in medicine to kill cancerous cells. Most medical devices require
sterilization after they are packaged, and another trend has been the move to sterilization by
__________________ radiation as opposed to other methods such as ethylene oxide gas. Advantages
of gamma irradiation include ______________, cost-effectiveness, and the elimination of the need for
special packaging. Chemical reaction rates are greatly affected by changes in temperature,
_____________________, and concentration, and by the presence of a catalyst. In contrast, nuclear
reaction rates remain ____________________ regardless of such changes. In fact, the half-life of any
particular radioisotope is constant. Because of this, radioisotopes, especially carbon-14, can be used to
determine the ____________ of an object. The process of determining the age of an object by
measuring the amount of a certain radioisotope remaining in that object is called radiochemical dating.
EFFECTS OF NUCLEAR REACTIONS
Any exposure to radiation can damage living ____________. Gamma rays are very dangerous because
they penetrate ______________________ and produce unstable and reactive molecules, which can
then disrupt the normal functioning of cells. The amount of radiation the body absorbs (a dose) is
measured in units called rads and ____________. Everyone is exposed to radiation, on average 100–
300 millirems per year. A dose exceeding ____________ rem can be fatal.
Atomic Theory, The Mole, and Nuclear Chemistry- Practice Test
1. Given the work of Dalton, please circle the postulate(s) that have since been proven to be incorrect.
Explain what we now know to be the true case.
[] All atoms of a specific element are identical.
[] Compounds consist of atoms of different elements combined together.
[] Atoms of different elements have different masses.
Directions: For the scientist listed below, explain what was done in the experiment, what knowledge
was developed as a result,
2. Rutherford ___________________________________________________________
3. Thomson ____________________________________________________________
Directions: Fill in the table for the following isotopes.
Isotope
Atomic #
Mass #
Protons
4.
H-1
5.
Cu-65
6.
18
40
7.
19
9
Neutrons
Electrons
8. What is the charge of a beta particle?
Directions: Solve the following problems be sure to include the correct unit with your final answer.
9. Given the equation:
X  24 He + 220
84 Po The nucleus represented by X is
10. How many moles of sodium are 6.02 x 10 23 atoms of sodium?
11. What is the mass of 6 mols of Carbon?
12. How many atoms are in 45g of Neon?
Multiple Choice Practice
13. What is the approximate formula mass of Ca(NO3)2
a. 70
c. 102
b. 82
d. 150
e. 164
14. How many molecules are in 1 mole of water?
a. 3
c. 6.02x1023
b. 54
d. 2(6.02x1023)
e. 3(6.02x1023)
15. How many atoms are represented in the formula Ca3(PO4)2
a. 5
c. 9
b. 8
d. 12
e. 13
16. Four grams of hydrogen gas at STP contain
a. 6.02x1023 atoms
b. 12.04x1023atoms
c. 12.04x1046atoms
d. 1.2x1022molecules
e. 12.04x1023molecules
17. What is the mass in grams of 1 mole of KAl(SO4)2*12H2O
a. 132
c. 394
b. 180
d. 474
e. 516
18. Compared to the charge and mass of a proton, an electron has
a. the same charge and a smaller mass
b. the same charge and the same mass
c. an opposite charge and a smaller mass
d. an opposite charge and the same mass
19. When alpha particles are used to bombard gold foil, most of the alpha particles pass through
undeflected. This result indicates that most of the volume of a gold atom consists of ____.
a. deuterons
c. protons
b. neutrons
d. unoccupied space
20. A proton has approximately the same mass as
a. a neutron
b. an alpha particle
c. a beta particle
d. an electron
21. A neutron has approximately the same mass as a
a. an alpha particle
b. a beta particle
c. an electron
d. a proton
22. Which symbols represent atoms that are isotopes?
a. C-14 and N-14
b. O-16 and O-18
c. I-131 and I-131
d. Rn-222 and Ra-222
23. Which atom contains exactly 15 protons?
a. P-32
b. S-32
c. O-15
d. N-15
24. An ion with 5 protons, 6 neutrons, and a charge of 3+ has an atomic number of
a. 5
b. 6
c. 8
d. 11
25. What is the mass number of an atom which contains 28 protons, 28 electrons, and 34 neutrons?
a. 56
b. 62
c. 90
d. 28
26. What is the total number of atoms represented in the formula CuSO4 . 5H2O?
a. 8
b. 13
c. 21
27. What is the gram formula mass of K2CO3?
a. 138 g
b. 106 g
d. 27
c. 99 g
d. 67 g
28. What is the total number of atoms contained in 2.00 moles of nickel?
a. 58.9
c. 6.02 x 1023
b. 118
d. 1.2 x 1024
29. What is the total number of moles of hydrogen gas contained in 9.03 x 1023molecules
a. 1.5 moles
c. 6.02 moles
b. 2.00 moles
d. 9.03 moles
30. What is the mass in grams of 3.0 x 1023 molecules of CO2?
a. 22 g
c. 66 g
b. 44 g
d. 88 g
31. The amount of substance having 6.022 x 1023 of any kind of chemical unit is called a(n):
a. formula
c. mole
b. mass number
d. atomic weight
32. The total number of atoms in the formula of aluminum dichromate, Al2(Cr2O7)3 is:
a. 5
b. 29
c. 17
d. 11
33. The total number of OXYGEN atoms in the formula of aluminum dichromate, Al2(Cr2O7)3 is:
a. 21
b. 10
c. 29
d. 7
34. The formula mass of calcium hydroxide, Ca(OH)2 is:
a. 57.05 grams
b. 74.10 grams
c. 128 grams
d. 97.07 grams
35. The formula mass of ammonium chlorate, NH4ClO3 is:
a. 101.5 g
b. 78.06 g
c. 211.43 g
d. 172.40 g
36. What is the molar mass of the gas butane, C4H10?
a. 13.02 grams
b. 485.2 grams
c. 68 24 grams
d. 58.14 grams
37. The molar mass of sodium chloride, NaCl is:
a. 69.71 grams
b. 2 grams
c. 6.022 x 1023 grams
d. 58.44 grams
38. The formula mass of magnesium hydroxide, Mg(OH)2 is:
a. 42.33 grams
c. 41.32 grams
b. 58.33 grams
d. 5 grams
39. What is the mass in grams of 3 moles of water molecules, H2O?
a. 54.06 grams
c. 0.166 grams
b. 21.02 grams
d. 6.01 grams
40. What is the mass of 4 moles of hydrogen molecules (H2)?
a. 4.04 grams
c. 3.96 grams
b. 8.08 grams
d. 1.98 grams
41. What is the mass in grams of 10 moles of ammonia, NH3?
a. 170.4 grams
c. 1.704 grams
b. 0.587 grams
d. 27.04 grams
42. How many moles of water molecules, H2O, are present in a 42 gram sample of water?
a. 23.98 moles
c. 2.33 moles
b. 0.429 moles
d. 757 moles
43. How many moles of methane molecules, CH4, are in 80 grams of methane?
a. 0.201 moles
c. 6.022 x 1080 moles
b. 4.98 moles
d. 1284 moles
44. How many moles of calcium hydroxide, Ca(OH)2 are in 150 grams of the compound?
a. 2.02 moles
c. 0.494 moles
b. 224.1 moles
d. 11115 moles
45. About how many atoms of helium would be found in 2 grams of helium?
a. 4.00260
c. 2
23
b. 6.02 x 10
d. 3.01 x 1023
46. By knowing the number of electrons in a neutral atom, you should also be able to determine
a. the number of neutrons in the neutral atom
b. the number of protons in the neutral atom
c. the atomic number of the neutral atom
d. the mass of the neutral atom
e. two of these
47. Which of the following arrangements represent ions?
i.
ii.
iii.
iv.
v.
12 protons, 12 neutrons, 11 electrons
12 protons, 11 neutrons, 12 electrons
11 protons, 12 neutrons, 12 electrons
11 protons, 12 neutrons, 11 electrons
12 protons, 12 neutrons, 12 electrons
a. 1 and 2
b. 1, 3, and 4
c. 1 and 3
d. 2 and 3
e. all of these are ions
48. Which of the following arrangements represent different isotopes of the same element?
i.
ii.
iii.
iv.
v.
12 protons, 11 neutrons, 12 electrons
11 protons, 12 neutrons, 11 electrons
10 protons, 12 neutrons, 12 electrons
11 protons, 12 neutrons, 10 electrons
12 protons, 12 neutrons, 12 electrons
a. 1 and 5
b. 2 and 4
c. 2, 3, 4 and 5
d. all of these qualify
e. None of these qualify
49. The average mass of a magnesium atom is 24.31. If you were able to select and measure a
single atom of magnesium, the chance that you would select an atom of mass 24.31 is about:
a. 0%
d. greater than 50%
b. 0.31%
e. 100%
c. 24.31%
50. How many oxygen atoms are there in one formula unit of Al2(SO4)3?
a. 3
c. 7
b. 4
d. 12
e. 24
51. If the abundance of 6Li (6.015121 amu) is 7.500% and the abundance of 7Li (7.016003 amu) is
92.500%, what is the average atomic mass?
a. 6.0750 amu
c. 6.9250 amu
b. 6.0902 amu
d. 6.9409 amu
52. Which of following is not true of the carbon-14 atom?
a. It has six protons
b. It has an average mass of 12.011 amu.
c. It has six electrons
d. It has eight neutrons
e. It is the less common than carbon-12
53. A particle with 15 protons and 18 electrons would be symbolized as:
a. Ar
c. P3b. Ar3d. P3+
54. Which of these is the correct number of particles in this nuclide?
a. 34 protons, 79 neutrons, 2 electrons
b. 34 protons, 45 neutrons, 32 electrons
c. 34 protons, 45 neutrons, 2 electrons
d. 34 protons, 45 neutrons, 36 electrons
e. 34 protons, 113 neutrons, 36 electrons
79
34
e.
Ar3+
Se 2
55. Which of the following have equal numbers of neutrons?
a. I, II and III
b. II and III
c. I and V
d. I and IV
e. II, III and IV
56. A particle X contains 10 electrons, seven neutrons and has a net charge of 3-. The particle is:
a. a nitride ion
d. a neon ion
b. obviously polyatomic
e. none of these are correct
c. an oxide ion
57. Ions are formed in chemical reactions by:
i. Gaining electrons
ii. Losing electrons
iii. Gaining protons
iv. Losing protons
v. All of these
a. 1 and 2 are correct
b. 3 and 4 are correct
c. 5 is correct
d. 1 and 3 are correct
e. 2 and 4 are correct
58. The number of errors contained in the table below is:
Nuclide
protons
neutrons
electrons
mass
Sodium-23
11
12
11
23
Cobalt-59
27
22
27
59
Tungsten-184
74
110
184
184
Fluorine-19
a. one
b. two
10
10
19
9
c. three
d. four
e. five
59. The element hafnium (Hf) has five stable isotopes. The correct number of nuclear particles in
an atom of hafnium-178 is:
a. 72 protons, 178 neutrons
d. 72 protons, 106 neutrons
b. 72 protons, 72 electrons
e. 72 protons, 106 neutrons, 72
c. 106 protons, 72 neutrons
electrons
60. J.J. Thomson's model of the atom can be summarized with the visual image of:
a. planets orbiting the sun
d. a small central nucleus and an
b. plum pudding
electron cloud
c. bees around a hive
e. none of the above
61.
10
5
B + _____  13 H + 2 24 He In the equation shown here, the missing particle is:
a.
b.
1
1
1
0
H
n
c.
d.
o
1
1
1
e.
e
p
62. Identify the missing particle in the following nuclear reaction:
37
38
a. 18 Ar
b. 18 Ar
c.
37
19
36
18
K → _____ +
Ar
4
2
0
1
He
e
d.
37
20
Ca
63. For the most common types of radioactive decay, the order of least penetrating to human tissue,
to most penetrating to human tissue is:
a. gamma, beta, alpha
c. beta, gamma, alpha
b. alpha, beta, gamma
d. gamma, alpha, beta
64. Very large nuclei tend to be unstable because of the:
a. repulsive forces between protons
b. attraction of protons for neutrons
c. repulsive forces between neutrons
d. attraction of electrons for the positively charged nucleus
e. repulsive forces between electrons
65. An alpha () particle is essentially a ____________________ nucleus.
a. plutonium
c. hydrogen
b. helium
d. uranium
e. carbon-12
66. Phosphorus-15 has a half-life of 14 days. What proportion of the original phosphorus-15
remains after 8 weeks?
a. 1/2
c. 1/4
e. 1/8
b. 1/16
d. 1/32
67. The nuclide radium-226 is the daughter nuclide resulting from the  decay of what parent
nuclide?
a. radon-222
c. thorium-230
e. radium-225
b. polonium-214
d. thorium-228
68. An electron emitted from the nucleus during some kinds of radioactive decay is known as:
a. A gamma ray
c. A beta () particle
b. A positron
d. An alpha () particle
69. A process in which a very heavy nucleus splits into more-stable nuclei of intermediate mass is
called:
a. nuclear fission
d. nuclear fusion
b. radiocarbon dating
e. radioactive decay
c. a chain reaction