Download Isotopes of an atom have the same number of protons, but a different

Several nomenclatures are important:
● Nuclide: is any particular atomic nucleus with a specific atomic
number Z and mass number A, it is equivalently an atomic nucleus with a
specific number of protons and neutrons. Nuclides may be stable or
unstable and unstable nuclides are radioactive.
● Isotopes: is one series of nuclides have the same atomic number, but a
different number of neutrons. They exhibit the same chemical properties.
Examples : A carbon atom: It has 6 protons and 6 neutrons we call it
ʺcarbon-12“ 126C because it has an atomic mass of 12. One useful isotope
of carbon is ʺcarbon-14“, 146C which has 6 protons and 8 neutrons.
Another example is the oxygen isotopes 158O, 168O, 178O, 188O.
Comparison of Two Isotopes
● Isotones: nuclides having the same number of neutrons but different
atomic number. Example, 5926Fe, 6027Co, 6229Cu each having 33 neutrons.
● Isobars: nuclides with the same mass number, but different number of
protons and neutrons, example 6729Cu, 6730Zu are isobars having the same
mass number 67.
● Isomers: nuclides having the same number of protons and neutrons but
differing in energy states. Example 99Tc and 99mTc.
The nuclides, both stable and radioactive are arranged in the form of a
chart.
Comparison of Two Isobars
Comparison of Two Isomers
"Chart of Nuclides"
 Radioisotopes, Radionuclides: unstable isotopes which are
distinguishable by radioactive transformation.
 Radioactivity: the process in which an unstable isotope undergoes
changes until a stable state is reached and in the transformation emits
energy in the form of radiation (alpha particles, beta particles and
gamma rays).
 Radiation refers to particles or waves coming from the nucleus of the
atom (radioisotope or radionuclide) through which the atom attempts
to attain a more stable configuration.
 Electron volt:
1 eV is the energy acquired by an electron when accelerated through a
potential difference of 1 V.
This amount of energy is very small, so the energies of particles are
usually given in terms of: MeV (megaelectron volt)
KeV (kiloelectron volt)
1 MeV = 103 KeV = 106 eV
Nuclear stability
 The stability of the atoms depends (N/Z) ratio in the nucleus.
 Above the atomic number 82, all elements are radioactive.
 The nucleons (P or N) are in a state of continual motion (natural
isotopes)
 If additional N or a deficiency of N occurs, the atom attempts to
regain its stability by giving off either a photon, such as gamma ray, or
particle from the nucleus to attain a more stable (N/Z) ratio and the
nucleus is transformed into another.
 This phenomenon is known as radioactivity or radioactive decay
Radioactive decay
 Majority of nuclides are unstable and the unstable nuclei decay by
spontaneous fission, α-particle, β-particle, or γ-ray emission or electron
capture in order to achieve stable.
 The radio-nuclides decay to achieve the N/Z ratio of the nearest
possible stable nuclide.
 Radioactive decay by particle emission or electron capture changes
the atomic number.
 Radionuclides may decay by any one or a combination of five
process α decay, β- decay, β+decay, electron capture or isomeric
transition.
Radioactive decay
Mode of radioactive decay:
Radioactive decay
Is the process in which an unstable atomic nucleus spontaneously loses
energy by emitting ionizing particles and radiation.
This decay, or loss of energy, results in an atom of one type, called the
parent nuclide transforming to an atom of a different type, named the
daughter nuclide.
When an unstable nucleus decays, It may give out:-
Modes of nuclear decay
Alpha decay
α-emission
Beta decay
Negatron
β- emission
Electron capture
Positron
β+ emission
Nuclear fission
Gamma emission
Isomeric
transition
1. Alpha particle decay (α-decay):
● α-decay occurs in very heavy elements, for example, Uranium (U) and
Radium (Ra).
● Alpha particles are made of 2 protons and 2 neutrons bound together in
the nucleus. We can write them as 42α , or 42He, because they're the same
as a helium nucleus.
● This means that when a nucleus emits an alpha particle, its atomic
number decreases by 2 and its atomic mass decreases by 4.
231 Th + 4 He
Example: 23592U
90
2
● Alpha particles are relatively slow and heavy.
● Alpha particles emitted from a particular nuclide have the same energy.
α- Decay (α- emission)
 They have a low penetrating power - you can stop them with just a sheet of paper.
 Because they have a large charge, alpha particles ionize other atoms strongly.
Since alpha particles cannot penetrate the dead layer of the skin, they do not present a
hazard from exposure external to the body.
However, due to the very large number of ionizations they produce in a very short
distance, alpha emitters can present a serious hazard when they are in close proximity
to cells and tissues such as the lung. Special precautions are taken to ensure that alpha
emitters are not inhaled, ingested or injected.
2- Beta particle decay (β-decay):
● Beta particles have a charge of minus 1. This means that beta particles
are the same as an electron.
We can write them as β- or e-, because they're the same as an electron.
A. Negatron (β- ) emission:
 Nuclei with excess neutrons gain stability by conversion of a neutron
into a (proton + β- + v). v is an antineutrino which is needed to conserve
energy in the decay.
 There is no change in the mass number, but the atomic number
increases by one unit.
Example of β- decay:
generally: n → p +β-+ v
131 I
131 Xe + β- + v
53
54
Negatron (β- ) emission:
40
19K
 4020Ca + β- + antineutrino
B. Positron or β+ Decay:
 This process occur with neutron deficient or proton rich nuclei.
 Conversion of a proton into neutron + positron (β+ ) + v (neutrino).
 Positrons are emitted with a continuous energy spectrum.
 After β+ particle emission, the daughter nuclide has an atomic number
that is one less than that of the parent.
 There is no change in the mass number but the atomic number is
reduced by one unit.
Examples:
64 Cu → 64 Ni + β+ + v
29
28
15 O → 15 N + β+ + v
8
7
generally: p → n + β+ + v
● They are fast, and light.
● Beta particles have a medium penetrating power - they are stopped by
a sheet of aluminium.
● Beta particles ionize atoms that they pass, but not as strongly as alpha
particles do.
Beta particles are much less massive and less charged than alpha
particles and interact less intensely with atoms in the materials they
pass through, which gives them a longer range than alpha particles.
3. Gamma-emission (γ rays):
● Gamma rays are waves, not particles.
● This means that they have no mass and no charge.
● In Gamma decay: atomic number unchanged, atomic
mass unchanged.
● Gamma rays have a high penetrating power - it takes
a thick sheet of metal such as lead to reduce them.
● Gamma rays do not directly ionize other atoms,
although they may cause atoms to emit other particles
which will then cause ionization.
● We don't find pure gamma sources - gamma rays are
emitted alongside alpha or beta particles.
Gamma radiation
Alpha particles are easy to stop, gamma
rays are hard to stop.
Mode of radioactive decay:
Type of
Radiation
Alpha
particle
Beta
particle
Gamma ray
Symbol
or
Charge
+2
-1
0
Speed
slow
fast
Very fast
Ionising ability
high
medium
0
Penetrating
power
low
medium
high
Stopped by:
paper
aluminium
lead
234
92U
230
90Th
 Determine whether alpha or beta decay occurs in the reaction in
which lead-210 decays to bismuth-210.
210
210 Bi + A X
Pb

82
83
Z
210 Bi + 0 β
Pb

82
83
-1
210
Negatron decay β-
 Identify the decay particle emitted and the decay process that
occurs when protactinium-231 decays to actinium-227.
231 Pa
91
 22789Ac + AZX
227 Ac + 4 He
Pa

91
89
2
231
Alpha (α)-decay