A simplified textbook for beginners in chemistry especially students in colleges of education, polytechnics and first year students in the university.

1. C H A P T E R O N E
A T O M I C A N D N U C L E A R S T R U C T U R E
To begin with, the term "nuclear chemistry" is a paradox. Chemical
changes involve the transfer or sharing of valence electrons. However, the
usual properties of nuclei—mass, atomic number, and nuclear structure—
bear no direct relation to chemical reactions. Consequently, there can be
no direct relationship between the chemical and nuclear properties of
atoms.
On the other hand, a wide variety of phenomena are of interest to
chemists either because certain nuclear properties provide new chemical
tools or because differences in nuclei actually produce subtleties of
chemical behavior. Thus, nuclear chemistry includes any of the
relationships between atomic and nuclear structure of importance to a
chemist.
In general, the nuclear chemist is concerned with those properties
involving similarities and differences among the isotopes of a given
element. It should be stressed that, in addition to stable isotopes, the
nuclear chemist studies radioactive isotopes by the application of the
various techniques of radio- chemistry and radiation chemistry. We often
use the term "radiochemistry" to describe work with radioactive atomic
species, whereas radiation chemistry is now limited to chemical effects
brought about by radiation interacting with a system.
Nuclear chemistry, or radioactivity, differs from other branches of
chemistry in that the important changes occur in the nucleus. These nuclear
changes also are represented by chemical equations. However, because the

2. isotopes of the same element may, from a nuclear standpoint, be very different in
reactivity, it is necessary that the equations show which isotopes are involved.
Table 1.0. Comparison of Chemical Reactions and Nuclear Reactions
Chemical Reactions Nuclear Reactions
1. Atoms are rearranged by the
breaking and forming of
chemical bonds.
Elements (or isotopes of the
same elements) are converted
from one to another.
2. Only electrons in atomic or
molecular orbital are involved
in the breaking and forming of
bonds.
Protons, neutrons, electrons, and
other elementary particles may
be involved.
3. Reactions are accompanied by
absorption or release of
relatively small amounts of
energy.
Reactions are accompanied by
absorption or release of
tremendous amounts of energy.
4. Rates of reaction are influenced
by temperature, pressure,
concentration, and catalysts.
Rates of reaction normally are
not affected by temperature,
pressure, and catalysts.
Both chemical and nuclear reactions are depicted by a complete chemical
equation. However, two major rules guide writing the chemical equation of
nuclear reaction:
(i) The sum of the mass numbers of the reactants must be equal the sum of mass
number of the products
(ii) The sum of atomic number of the reactions must be equal to the atomic
number of the products, this maintain charge balance.
The Structure of the Atom
As is well known, our present concept of the atom includes the notion that
the atom consists of a dense nucleus containing protons and neutrons and

3. surrounded by electrons occupying certain positions, or following certain
paths of motion.
Each element can be represented by the notation 𝑋𝑍
𝐴
, where A, the mass
number, is the sum of the number of protons and the number of neutrons, and Z,
the atomic number, is the number of protons. The protons and neutrons that
make up the nucleus of an atom are called nucleons, and an atom with a
particular number of protons and neutrons is called a nuclide. Nuclides with the
same number of protons but different numbers of neutrons are called isotopes.
Isotopes can also be represented by an alternative notation that uses the name of
the element followed by the mass number, such as carbon-12. The stable isotopes
of oxygen, for example, can be represented in any of the following ways:
Because the number of neutrons is equal to A − Z, we see that the first
isotope of oxygen has 8 neutrons, the second isotope 9 neutrons, and the third
isotope 10 neutrons. Isotopes of all naturally occurring elements on Earth are
present in nearly fixed proportions, with each proportion constituting an isotope’s
natural abundance. For example, in a typical terrestrial sample of oxygen, 99.76%
of the O atoms is oxygen-16, 0.20% is oxygen-18, and 0.04% is oxygen-17.
Any nucleus that is unstable and decays spontaneously is said to be
radioactive, emitting subatomic particles and electromagnetic radiation. The
emissions are collectively called radioactivity and can be measured. Isotopes that
emit radiation are called radioisotopes. Table 1.1 below shows the basic
constituents of an atom.

4. Table 1.1. Basic constituents of an atom.
The ratio of number of neutron to proton in any nucleus confirms the
stability of the nucleus and also influence nuclear reaction is called neutron –
proton ratio. The neutron – proton ratio of an element dictates which element
will naturally undergoes radioactivity or not.
Neutron - Proton Ratio and Nuclear Stability
The principal factor that determines whether a nucleus is stable is the
neutron-to-proton ratio (n/p). For stable atoms of elements having low atomic
number, the n/p value is close to 1. As the atomic number increases, the neutron-
to-proton ratios of the stable nuclei become greater than 1. This deviation at
higher atomic numbers arises because a larger number of neutrons is needed to
counteract the strong repulsion among the protons and stabilize the nucleus. The
following rules are useful in predicting nuclear stability:
1. Nuclei that contain 2, 8, 20, 50, 82, or 126 protons or neutrons are generally
more stable than nuclei that do not possess these numbers. For example, there
are 10 stable isotopes of tin (Sn) with the atomic number 50 and only 2 stable
isotopes of antimony (Sb) with the atomic number 51. The numbers 2, 8, 20, 50,
82, and 126 are called magic numbers. The significance of these numbers for
nuclear stability is similar to the numbers of electrons associated with the very
stable noble gases (that is, 2, 10, 18, 36, 54, and 86 electrons).
2. Nuclei with even numbers of both protons and neutrons are generally more
stable than those with odd numbers of these particles (Table 1.2).

5. 3. All isotopes of the elements with atomic numbers higher than 83 are
radioactive. All isotopes of technetium (Tc, Z = 43) and promethium (Pm, Z = 61)
are radioactive.
Table 1.2. Number of stable isotopes with even and odd numbers of protons & neutrons
Fig. 1.2 shows a plot of the number of neutrons versus the number of
protons in various isotopes. The stable nuclei are located in an area of the graph
known as the belt of stability. Most radioactive nuclei lie outside this belt. Above
the stability belt, the nuclei have higher neutron-to-proton ratios than those
within the belt (for the same number of protons). To lower this ratio (and hence
move down toward the belt of stability), these nuclei undergo the following
process, called b-particle emission:
Below the stability belt, the nuclei have lower neutron-to-proton ratios than those
in the belt (for the same number of protons). To increase this ratio (and hence
move up toward the belt of stability), these nuclei either emit a positron
or undergo electron capture. An example of positron emission is
Electron capture is the capture of an electron—usually a 1s electron—by the
nucleus. The captured electron combines with a proton to form a neutron so that
the atomic number decreases by one while the mass number remains the same.
This process has the same net effect as positron emission:

6. Fig. 1.2. Plot of neutrons versus protons for various stable isotopes, represented by dots. The straight
line represents the points at which the neutron-to-proton ratio equals 1. The shaded area represents the
belt of stability.
Radioactivity
Radioactivity is a phenomenon in which some elements emit small particles
called radiation, to form another element. This is in contrast to the accepted
Dalton postulate of indestructibility of an atom. However, only elements with
unstable nuclei known as radioactive are capable of undergoing natural
radioactivity while stable nuclei do not. All elements having atomic number

7. greater than 83 are radioactive and they undergo nuclear transmutation (nuclear
reaction) which differ significantly from ordinary chemical reactions.
Natural Radioactivity (spontaneous disintegration)
This is natural radioactivity caused by the instability of an atom. The
phenomenon of radioactivity was discovered by Antoine Henri Becquerel in 1896.
He discovered that photographic plates develop bright spots when exposed to
uranium minerals, and he concluded that the minerals give off some sort of
radiation.
Fig. 1.3. Separation of the radiation from a radioactive material (uranium mineral). The radiation
separates into alpha (α), beta (β), and gamma (𝛾) rays when it passes through an electric field.
The radiation from uranium minerals was later shown to be separable by electric
(and magnetic) fields into three types, alpha (α), beta (β), and gamma (γ) rays
(Figure 1.3).
Alpha Particles
Alpha rays bend away from a positive plate and toward a negative plate,
indicating that they have a positive charge. The alpha particle is the heaviest. It is
produced when the heaviest elements decay. Alpha and beta rays are not waves.
They are high-energy particles that are expelled from unstable nuclei. In the case

8. of alpha radiation, the high energy particles leave the nucleus. The alpha particle
is a helium atom and contains two neutrons and two protons. It leaves the
nucleus of an unstable atom at a speed of 16,000 kilometers per second, around a
tenth the speed of light. The alpha particles are relatively large and heavy. As a
result, alpha rays are not very penetrating and are easily absorbed. A sheet of
paper or a 3-cm layer of air is sufficient to stop them. Its energy is transferred
within a short distance to the surrounding media. However, its short flight
knocks about 450,000 electrons out of the surrounding atoms. The alpha particle
emitter will not penetrate the outer layer of our skin, but is dangerous if inhaled
or swallowed. The delicate internal workings of the living cell forming the lining
of the lungs or internal organs, most certainly will be changed (mutated) or killed
outright by the energetic alpha particle. The number of lung cancer cases among
uranium miners from inhaled and ingested alpha sources is much higher than
those of the public at large. Radon, the gas produced by the decay of radium-226,
also emits alpha particles, which poses a hazard to lungs and airways when
inhaled. Homes built in areas with high ground radioactivity should be tested for
radon buildup in enclosed basement spaces.
An example of a transmutation takes place when uranium decays into the
element thorium (Th) by emitting an alpha particle, as depicted in the following
equation:
𝑈 →92
238
𝐻𝑒 + 𝑇ℎ90
234
2
4
More examples of reactions involving emission of alpha particles are shown below
𝑅𝑎 →88
226
𝐻𝑒 + 𝑅𝑛86
222
2
4
𝑃𝑜 →84
210
𝐻𝑒 + 𝑃𝑏82
206
2
4
In general, alpha decay process is summarized below
𝑋 → (𝑍
𝐴
)𝑌 + 𝐻𝑒 + 𝑄2
4
𝑍−2
𝐴−4

9. Where:
A is the mass number
Z is the atomic number
Q is the kinetic energy of the decay product
Beta Particles
Beta rays bend in the opposite direction to alpha particles, indicating that
they have a negative charge; they are now known to consist of high-speed
electrons. Beta rays are much lighter energy particles. The beta particle is an
energetic electron given off by the nucleus of unstable isotopes to restore an
energy balance. They leave the nucleus at a speed of 270,000 kilometers per
second. They can be stopped, for instance, by an aluminum sheet a few
millimeters thick or by 3 meters of air. The RS-500 can detect most energetic
beta particles through the case. Weaker beta particles can be detected through the
tube window. Although the beta particle is around 8000 times smaller than the
alpha particle, it is capable of penetrating much deeper into living matter. Each
encounter with a living cell, and there may be many before the beta energy is
dissipated, is likely to dam age some of the chemical links between the living
molecules of the cell or cause some permanent genetic change in the cell nucleus.
If the damage occurs within the generative cells of the ovaries or testes, the
damage may be passed to new generations. The normal background radiation
level must contribute to the mutation of the gene pool. Most mutations are
undesirable with a very few leading to "improvements". Any increase in the
background level of radiation should be considered harmful. Shown below are
some examples of beta emission:

10. The beta decay process is summarized as follows
𝑋 → (𝑍
𝐴
)𝑌 + 𝛽 + 𝑄−1
0
𝑍+1
𝐴
Where:
A is the mass number
Z is the atomic number
Q is the kinetic energy of the decay product
Note that beta emission leads to an increase in the atomic number by 1, the mass
number remain unchanged.
Gamma rays
Gamma rays are unaffected by electric and magnetic fields: they have been shown
to be a form of electromagnetic radiation that is similar to x- rays, except they are
higher in energy with shorter wavelengths (about 1pm). It is capable of damaging
living cells as it slows down by transferring its energy to surrounding cell
components. Gamma ray sources are used to find flaws in pipes and vessels and to
check the integrity of welds in steel.
Uranium minerals contain a number of radioactive elements, each emitting
one or more of these radiations. Uranium-238, the main uranium isotope in
uranium minerals, emits alpha rays and thereby decays, or disintegrates, to
thorium-234 nuclei. A sample of uranium-238 decays, or disintegrates,
spontaneously over a period of billions of years. After about 30 billion years, the
sample would be nearly gone. Strontium-90, formed by nuclear reactions that
occur in nuclear weapons testing and nuclear power reactors, decays more

11. rapidly. A sample of strontium-90 would be nearly gone after several hundred
years. In either case, it is impossible to know when a particular nucleus will decay,
except if precise information about the rate of decay of any radioactive sample is
given.
In gamma emission, there is no change in either the mass number or atomic
number. The gamma symbol (𝛾) is indicated in the nuclear equation by adding to
the products as shown in the equations below.
𝑇ℎ →90
234
𝑃 + 𝛽 + 𝛾−1
0
91
234
𝑈 →92
238
𝑇ℎ + 𝐻𝑒 + 𝛾2
4
90
234
Table 1.3. Products of natural radioactivity
Artificial Radioactivity or Nuclear Transmutation
The scope of nuclear chemistry would be rather narrow if study were
limited to natural radioactive elements. An experiment performed by Rutherford
in 1919, however, suggested the possibility of producing radioactivity artificially.
When he bombarded a sample of nitrogen with 𝛼 particles, the following reaction
took place:
𝑁 +7
14
𝛼 → 𝑂8
17
+ 𝑃1
1
2
4
An oxygen-17 isotope was produced with the emission of a proton. This reaction
demonstrated for the first time the feasibility of converting one element into
another, by the process of nuclear transmutation. Nuclear transmutation differs

12. from radioactive decay in that the former is brought about by the collision of two
particles.
The preceding reaction can be abbreviated as 𝑁 𝛼, 𝑝 𝑂8
17
.7
14
Note that in
the parentheses the bombarding particle is written first, followed by the ejected
particle.
The reactions below further illustrates artificial radioactivity.
𝐿𝑖 +3
6
𝑛 → 𝐻𝑒2
4
+ 𝐻1
3
𝑜
1
𝑈 +92
238
𝑛 → 𝑃𝑢94
239
+ 𝐻 + 2 𝛽−1
0
1
3
𝑜
1
𝑆 +16
32
𝑛 → 𝑃15
32
+ 𝐻1
1
𝑂
1
Example 1.1.
Write the balanced equation for the nuclear reaction 𝐹𝑒 𝑑, 𝛼 𝑀𝑛25
54
26
56
, where d
represents the deuterium nucleus (that is, 𝐻1
2
).
Strategy
To write the balanced nuclear equation, remember that the first isotope 𝐹𝑒26
56
is
the reactant and the second isotope 𝑀𝑛25
54
is the product. The first symbol in
parentheses (d) is the bombarding particle and the second symbol in parentheses
(a) is the particle emitted as a result of nuclear transmutation.
Solution
The abbreviation tells us that when iron-56 is bombarded with a deuterium
nucleus, it produces the manganese-54 nucleus plus an 𝛼 particle. Thus, the
equation for this reaction is
𝐹𝑒26
56
+ 𝐻1
2
→ 𝛼2
4
+ 𝑀𝑛25
54

13. Although light elements are generally not radioactive, they can be made so
by bombarding their nuclei with appropriate particles. As we saw earlier, the
radioactive carbon-14 isotope can be prepared by bombarding nitrogen-14 with
neutrons. Tritium 𝐻,1
3
is prepared according to the following bombardment:
Many synthetic isotopes are prepared by using neutrons as projectiles. This
approach is particularly convenient because neutrons carry no charges and
therefore are not repelled by the targets—the nuclei. In contrast, when the
projectiles are positively charged particles (for example, protons or 𝛼 particles),
they must have considerable kinetic energy to overcome the electrostatic
repulsion between themselves and the target nuclei. The synthesis of phosphorus
from aluminum is one example:
A particle accelerator uses electric and magnetic fields to increase the kinetic
energy of charged species so that a reaction will occur (Figure 1.4). Alternating
the polarity (that is, + and -) on specially constructed plates causes the particles
to accelerate along a spiral path. When they have the energy necessary to initiate
the desired nuclear reaction, they are guided out of the accelerator into a collision
with a target substance.

14. Figure 1.4. Schematic diagram of a cyclotron particle accelerator. The particle (an ion) to be
accelerated starts at the center and is forced to move in a spiral path through the infl uence of electric and
magnetic fi elds until it emerges at a high velocity. The magnetic fi elds are perpendicular to the plane of
the dees (so-called because of their shape), which are hollow and serve as electrodes.
The Transuranium Elements
Particle accelerators made it possible to synthesize the so-called transuranium
elements, elements with atomic numbers greater than 92. Neptunium (Z = 93) was
first prepared in 1940. Since then, 24 other transuranium elements have been
synthesized. All isotopes of these elements are radioactive. Table 1.4 lists the
transuranium elements up to Z = 111 and the reactions through which they are
formed.

15. Table 1.4. The transuranium elements
Exercise 1.
Element 118, known currently by its IUPAC systematic name ununoctium
(symbol: Uuo), was first created in 2006 in Dubna, Russia. The nuclear reaction
used to produce this element was 𝐶𝑓 𝐶𝑎20
48
, 𝑋 𝑈𝑢𝑜118
294
.98
249
Determine the product
X and write the balanced equation for this nuclear reaction.
EQUATIONS INVOLVING NUCLEAR REACTIONS
To discuss nuclear reactions in any depth, we need to understand how to write
and balance the equations. Writing a nuclear equation differs somewhat from
writing equations for chemical reactions. In addition to writing the symbols for
various chemical elements, we must also explicitly indicate protons, neutrons, and

16. electrons. In fact, we must show the numbers of protons and neutrons present in
every species in such an equation.
The symbols for elementary particles are as follows:
As earlier mentioned, the superscript in each case denotes the mass number (the
total number of neutrons and protons present) and the subscript is the atomic
number (the number of protons). Thus, the ―atomic number‖ of a proton is 1,
because there is one proton present, and the ―mass number‖ is also 1, because
there is one proton but no neutrons present. On the other hand, the ―mass
number‖ of a neutron is 1, but its ―atomic number‖ is zero, because there are no
protons present. For the electron, the ―mass number‖ is zero (there are neither
protons nor neutrons present), but the ―atomic number‖ is -1, because the electron
possesses a unit negative charge.
The symbol 𝑒−1
0
represents an electron in or from an atomic orbital. The symbol
𝛽−1
0
represents an electron that, although physically identical to any other
electron, comes from a nucleus (in a decay process in which a neutron is
converted to a proton and an electron) and not from an atomic orbital. The
positron has the same mass as the electron, but bears a +1 charge. The 𝛼 particle has
two protons and two neutrons, so its atomic number is 2 and its mass number is
4.
In balancing any nuclear equation, we observe these rules:
• The total number of protons plus neutrons in the products and in the reactants
must be the same (conservation of mass number).
• The total number of nuclear charges in the products and in the reactants must
be the same (conservation of atomic number).
For example, in

17. 1. 𝐴 +𝑏
𝑎
𝐵 = 𝐶𝑦
𝑥
𝑑
𝑐
The algebraic sum:
a + c must be equal to x
b + d must be equal to y
and in
2. 𝑈 +𝑏
𝑎
𝑊 = 𝑋𝑓
𝑒
+ 𝑌𝑛
𝑚
𝑑
𝑐
The algebraic sum:
a + c must be equal to e + m
b + d must be equal to f + n
Example 1.2
Find the missing number (x, y) in the following nuclear reactions.
i. 𝐹 +9
19
𝐻 → 𝑁𝑒𝑥
20
1
𝑦
ii. 𝑁 +7
𝑥
𝑛 → 𝐶𝑦
14
0
1
+ 𝐻1
1
iii. 𝐶 →6
14
𝑒 + 𝑋7
14
𝑥
𝑦
Solution
i. 19 + y = 20
y = 20 -19
= 1
9 + 1 = x
x = 10
∴ 𝐻 = 𝐻1
1
𝑎𝑛𝑑 𝑁𝑒 = 𝑁𝑒10
20
𝑥
20
1
𝑦
ii. x + 1 = 14 + 1
x+ 1 = 15
x = 15-1
x =14
7 + 0 = y + 1
y = 7-1

18. y= 6
∴ 𝑁 = 𝑁7
14
𝑎𝑛𝑑 𝐶 =𝑦
14
𝐶6
14
7
𝑥
iii. 14 = 14 + y
y = 14 – 14
= 0
6 = x + 7
x = 6 – 7
= -1
∴ 𝑒 = 𝑒−1
0
𝑥
𝑦
When a heavy nucleus breaks down or disintegrate into simpler and lighter
nuclei, they release at the same time enormous amount of energy. Alpha particle
( 𝐻𝑒2
4
) and beta particle ( 𝑒−1
0
) earlier discussed are the two main products of such
nuclei disintegration and are used in balancing nuclear equations.
Q. Show that the mass number and the total charge are both conserved in the
natural disintegration of 𝑈:92
238
238U
Solution
The equation may be rewritten including all atomic numbers and mass numbers: