•
Radioactivity is the process in which an unstable atomic nucleus loses energy  
by emitting radiation in the form of particles or electromagnetic wave.  
OR Radioactivity is the spontaneous breaking up of unstable nuclei with the  
emission of one or more types of radiation  
OR Radioactivity is the spontaneous disintegration of the nucleus of unstable  
elements with the emission of radiations  
NB:  
•
•
•
Radioactivity is also called radioactive decay  
Disintegrated atom is called parent nuclide  
The new atom formed is called Daughter nuclide  
Terms used  
Matter  
•
Matter is anything that occupies space and has weight. Eg, water iron, meat,etc  
,
Element  
•
Is a pure substance that is made up of only one kind of atom and cannot be  
broken down into simpler parts by a chemical means.  
•
Atom  
•
For example, helium (  
H
), hydrogen (He), iron (Fe) etc  
Is the smallest particle of an element that has all the chemical characteristics of  
an element. For example, helium (  
H
), hydrogen (He), iron (Fe) etc  
Molecule  
•
Is a group of atoms. For example, water molecule (H2O), hydrogen molecules (H2)  
Strong Force  
•
Is the force that hold protons and neutrons present in the nucleus oppose and  
overcome repulsion between protons  
Binding Energy  
•
Is the energy that holds protons and neutrons present in the nucleus oppose  
and overcome repulsion between protons  
Nuclear Binding Energy  
•
Is the energy required to split the nucleus of an atom into its components  
Written by Geoffrey M Idebe (0688 082 089)  
Page 60  
Structure of Atom  
According to Rutherford atom  
“
Atom has a structure like a small solar system, in which the planet is electron and the  
place of the sun is taken by a small heavy positive charged particle called nucleus  
(Protons and Neutrons)” (see the fig. below)  
•
Therefore atoms are made up by subatomic (three types of) particles namely  
Protons(p), Neutrons(n) and Electrons(e)  
Protons  
•
•
Proton is the positively charged particle of an atom.  
It is denoted by small letter  
p
. its charge and its mass is +1.6 x 10-19 C and  
1.6726 x 10-27 kg respectively  
Neutrons  
•
•
Neutron is the neutral charged particle of an atom.  
It is denoted by small letter  
n
. Its charge and its mass are  
0
C and 1.6749 x 10-  
27 kg respectively  
Electrons  
•
•
An electron is the negatively charged particle of an atom.  
−19  
It is denoted by small letter  
e.  
Its charge and mass are -1.6 x 10  
C
and 9.1094  
x 10−31 kg respectively. The electron always revolve around the nucleus  
Atomic Number  
•
Atomic number is the number of protons present in a nucleus of a particular atom.  
•
It is denoted by capital letter  
Z
Mass Number  
•
•
Mass number is the sum of protons and neutrons particles.  
Also is called atomic mass/weight. It is denoted by capital letter A  
Mathematically  
:
A = Z + N  
•
In a given atom/elements (X) mass number (A) located as Superscript while  
퐴
atomic number (Z) located as Subscript. i.e  
푍푋  
Isotopy  
•
Is the existence of atoms of the same element with the same atomic number  
but differ in atomic mass.  
•
Elements which can form isotopy are called isotopic elements (isotopes)  
Written by Geoffrey M Idebe (0688 082 089)  
Page 61  
Isotopes  
•
Are the atoms of the same element having the same atomic number but  
different mass number  
Isotopic Elements and their Isotopes  
Elements  
Z
Isotopes  
A
Hydrogen  
1
Hydrogen - 1  
Deuterium  
Tritium  
1
2
3
Carbon  
Oxygen  
6
8
Carbon - 12  
Carbon - 13  
Carbon - 14  
Oxygen - 16  
Oxygen - 17  
Oxygen - 18  
12  
13  
14  
16  
17  
18  
Chlorine  
Uranium  
17  
92  
Chlorine - 35  
Chlorine - 37  
Uranium - 234  
Uranium - 235  
Uranium - 238  
Lead - 202  
Lead - 206  
Lead - 207  
Lead - 208  
35  
37  
234  
235  
238  
202  
206  
207  
208  
lead  
82  
NB:  
•
The different isotopes always differ by one neutron (1 0푛  
)
1
•
Isotopes of particular element/atom; the larger the mass number (A) the  
heaviest of element and vice versa  
Isobars  
•
I
sobar is the different elements having the same mass number but different  
atomic number.  
Isotones  
•
Isotones are different elements having the same number of neutrons.  
Example  
1
ퟑퟕ  
ퟏퟕ  
3. One isotope of chlorine has the symbol  
푪풍  
Calculate the number of neutrons in this isotope  
Soln: from  
A = Z + N  
→ 37 = 17 + 푁  
→ 37 − 17 = 20  
∴ 푇ℎ푒 푛푢푚푏푒푟 푛푒푢푡푟표푛푠 = 20  
Written by Geoffrey M Idebe (0688 082 089)  
Page 62  
Individual task – 3:1  
1.  
Tin (Sn) has a total of twenty-five isotopes; the lightest is represented by the  
symbol 108Sn50  
.
Given that all twenty-five isotopes of tine exist, write down the  
ퟏퟑퟐ  
푺풏)  
symbol for the heaviest tin isotopes (ANS:  
ퟓퟎ  
Stable Atom  
•
Is the atom whereby its binding energy is strong enough to hold nucleus of an  
atom together  
.
•
N.B: Stability of an atom decreases as the atomic number increases  
Unstable Atom  
•
I
s the atom whereby its binding energy is not strong enough to hold nucleus of  
an atom together  
.
Types of Radioactivity  
❖
❖
Natural radioactivity  
Artificial radioactivity  
Natural Radioactivity  
•
Is the process in which an unstable atomic nucleus loses energy by emitting  
radiation in the form of particles or electromagnetic wave  
OR  
•
•
Is the spontaneous disintegration of unstable atoms (nuclei).  
For example, unstable isotopes such that carbon-14 and heavy elements  
such as lead and uranium etc  
NB:  
✓
In natural radioactivity the nucleus of the elements disintegrate on their own accord  
✓
Materials exhibit radioactivity is called radioactive material  
✓
✓
In the periodic table all elements above lead exhibit natural radioactivity  
Examples of radioactive material are thorium (Th), uranium (U), Radon (Rn),  
Radium (Ra), Polonium (Po) etc  
How Natural Radioactivity Occurs?  
•
Natural radioactivity occurs when atomic nucleus has many number of protons  
in the nucleus, due to the law of charges, like charges repel therefore repulsion  
force is larger enough to overcome strong force (binding energy) resulting  
unstable atomic nucleus disintegrate (decay) into smaller nuclei (daughter  
nuclide) which are smaller and more stable than parent nuclide  
Nuclear Radiation  
•
Is the energy or particles or electromagnetic waves emitted by unstable atom  
(radioactive element)  
Written by Geoffrey M Idebe (0688 082 089)  
Page 63  
Types of Radiation  
➢
➢
➢
Alpha (  
Beta (β) particle  
Gamma (γ) rays  
훼
) particle  
Alpha Particle  
(
훼
)
•
Is the particle emitted by radioactive material which is equivalent to helium  
nucleus particle (4퐻푒),i.e  
휶
=
4퐻푒  
2
2
Effect on Nucleus  
•
•
•
When a radioactive nucleus emits an alpha particle its atomic number  
decreases by two and mass number decreases by 4.  
The effect tend to form other element and the nuclear equation is given by:  
퐴−4  
푍−2  
퐴푍푋  
4
→
푌
+ 2퐻푒  
Whereby:  
퐴푍푋  
Is parent nuclide  
Is daughter nuclide  
The parent nuclide can give more than one daughter nuclide  
➢
➢
➢
퐴−4  
푌
푍−2  
•
•
Example 1: Uranium-238 undergoes an alpha decay to produce thorium-234  
238  
4
Solution: 푈 →  
234푇ℎ + 퐻푒  
92  
90  
2
Example 2: Radium-222 undergoes an alpha decay to produce radon-218  
4
Solution:  
222푅푎→ 218푅푛 + 퐻푒  
88  
86  
2
Properties of Alpha Particles  
•
•
•
•
•
•
•
•
It is helium in nature  
It is a positively charged particle. it has relative charge of 2+  
It has very low penetrating power since it is the heaviest particle  
It can be stopped/shielding by a few cm of air, thin sheet of paper, skin, clothes etc  
It can cause some materials to fluorescence i.e. to give out light  
It affects/blackens photographic plate (film)  
It is a heaviest particle due to its biggest mass and charge  
It has very high ionizing power, since it is a heaviest particle  
❖
It is emitted up to speed of 0.1of light  
•
It can be deflected by electric and magnetic field  
Beta Particle (β)  
•
Is the particle emitted by radioactive material which is equivalent to electron  
(−1푒 ) (β =−1푒)  
0
0
Written by Geoffrey M Idebe (0688 082 089)  
Page 64  
Effect on Nucleus  
•
When a radioactive nucleus emits beta particle its atomic number increases by  
one (1)and mass number remains constant.  
•
The effect tend to form other element and the nuclear equation is given as:  
푨풁푿  
풁+푨ퟏ풀  
ퟎ
→
+ 풆  
−ퟏ  
•
•
Example 1: Carbon-14 undergoes beta decay to produce nitrogen-14  
14  
14  
−01푒  
Solution: 퐶 → 푁 +  
7
6
Example 2: Iodine-131 emits beta particles to produce xenon-131  
131  
Solution: 퐼 →  
53  
0
131푋푒  
+ −1푒  
54  
Properties of Beta Particles  
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
❖
It is electron in nature  
It is a negatively charged particle. It has relative charge of -1  
It has high kinetic energy electrons  
It has moderate penetrating power due to its low mass  
It can be stopped by a few mm of metals like aluminium, Plastic, glass, light metals etc  
It has moderate ionizing power due to its low mass  
It is emitted up to speed of 0.9C where C = 3 x 108 m/s  
It affects/blackens photographic plate (film)  
It causes some materials to fluorescence i.e. to give out light  
It has smaller mass and charge than the alpha particle  
It can be deflected by either electric or magnetic field  
N.B  
•
Beta particles have less ionizing powers compared to alpha particles. This is  
because beta particles have smaller mass than alpha particles  
Gamma Rays  
(
훾)  
•
•
Are electromagnetic waves with very short wavelengths and high frequencies  
It is released during emission of alpha or beta particle (γ). It is also called  
gamma radiation  
Effect on Nucleus  
•
When a radioactive nucleus emits gamma rays its atomic number and mass  
number remain the same.  
•
The effect tend to form other element and the nuclear equation is given by:  
퐴
퐴푍푋  
푍+1푌  
−01푒  
→
+
+
γ
Chemical reaction with alpha particle  
퐴−4  
푍−2  
퐴푍푋  
4
→
푌
+ 2퐻푒 + γ  
Written by Geoffrey M Idebe (0688 082 089)  
Page 65  
Example 1: Cobalt-60 by emitting a beta particle to produce nickel-60 and  
gamma rays  
ퟔퟎ  
ퟔퟎ  
푪풐  
−ퟎퟏ풆  
+
+
γ
→ 푵풊  
ퟐퟕ  
ퟐퟖ  
Example 2: Iodine-131 emits beta particles to produce xenon-131 and gamma rays  
ퟏퟑퟏ  
ퟓퟑ  
−ퟏퟎ풆  
ퟏퟑퟏ  
ퟓퟒ  
→
푿풆  
+
+
γ
푰
Properties of Gama Rays  
▪
▪
▪
▪
▪
They are electromagnetic waves in nature  
They are neutral in charge i.e have zero relative charge  
They have very high frequency electromagnetic radiation  
They have very high penetrating power since they have no mass  
They can be stopped by a thick layer of steel or concrete  
,
dense metal, but  
even a few cm of dense lead doesn't stop all of it  
They have lowest ionizing power since have no mass  
They have no mass since they are rays (radiations)  
They move with a speed of light i.e 3 x 108 m/s  
They affect/blacken photographic plate (film)  
▪
▪
▪
▪
▪
▪
They cause some material to fluorescence i.e. to give out light  
They cannot be deflected by electric field or magnetic field  
Consider the figure below showing the penetrating powers  
The figure below shows the deflection in an electric field  
➢
Alpha particles deflected toward south pole, beta particles deflected toward  
north pole while gamma rays is not deflected  
Written by Geoffrey M Idebe (0688 082 089)  
Page 66  
Individual task – 3:2  
1. Uranium 238푈 emits an alpha particle to become another element, as shown in  
92  
퐴
the following equation92238푈 → 푍푋 + 퐴푙푝ℎ푎 푝푎푟푡푖푐푒. Determine the value of A  
and Z (ANS: A = 234 , Z = 90)  
2. The element Thorium (Th) has atomic number 90 and mass number 234. The  
element decays by emitting a beta particle to form Protactinium (Pa). Write a  
nuclear equation for this decay  
(
ANS  
:
ퟐퟑퟒ푨 → ퟐퟑퟒ푷풂 +  
ퟎ풆)  
ퟗퟎ  
ퟗퟏ  
−ퟏ  
3. The following reaction is part of a radioactive series. Identify the reaction  
x
and  
determine the values of  
c
and  
z
ퟐퟏퟎ  
ퟐퟏퟎ  
(
ANS: x is beta particle, c = 206, z = 82)  
푨
푨
ퟖퟒ  
푪풁푸  
ퟖퟑ  
4. (ii) Define the terms isotope  
(ii) Uranium 238푈 decayed to Polonium ퟐퟐퟐ푷풐 by  
훼
-particle emission at each  
92  
stage via 234푇ℎ  
,
ퟐퟑퟎ푹풂 and ퟐퟐퟔ푹풏 . Follퟖoퟒwing this stage ퟐퟐퟒ푷풐 decayed to  
푥
풙
풛
ퟖퟒ  
ퟖퟔ풒푹풏  
by  
훽
-particle only  
(a)Write balanced equation of the stage decay process from 238푈 푡표 ퟐퟐퟔ푹풏  
92  
풛
and determine the value of x, y, z and q  
(b) Identify isotopes and isobars  
(ANS Isotopes is Radon;  
ퟐퟐퟔ푹풏 and ퟐퟐퟐ푹풏, Isobars is ퟐퟐퟐ푷풐 and ퟐퟐퟐ푹풏  
)
ퟖퟔ  
ퟖퟔ  
ퟖퟒ  
ퟖퟔ  
5. A uranium nucleus, U-238 with atomic number 92, emits two  
훼-particles and two  
훽
-particles and finally forms a thorium (Th) nucleus. Write the nuclear equation for  
ퟎ
ퟐퟑퟒ  
ퟗퟎ  
this process  
(
ퟐퟑퟖ푼  
→ ퟐퟒ푯풆 → ퟐ  
푻풉)  
−ퟏ풆 →  
ퟗퟐ  
ퟐ
6. Radioactive uranium 238푈 emits an  
훼-particle to become thorium. Thorium emits  
92  
a
훽
-particle to become praseodymium which then emits another  
훽
-particle. What  
are the atomic number, mass number and number of final atom produced?  
(ANS  
:
Uranium has atomic number 92 therefore the final product is uranium)  
Application of Natural Radioactivity (Radio isotopes)  
In hospital (medicine)  
(a) Gamma rays from cobalt 60 are used to sterilize surgical equipment  
(b) Radioactive sodium is used to monitor blood circulation  
(c) Used to trace and treat maligned growth. E.g. cancer and tumors  
(d) Used to measure correct patient dosages of radioactive pharmaceuticals  
(e) Used in molecular biology and genetics research.  
(f) Radioactive iodine 131 is used to monitor the function of thyroid gland  
In industry  
(a) Used to measure and control the thickness or density of metal and plastic sheets  
(b) Used in preservation of food by killing microorganisms that cause spoilage  
Written by Geoffrey M Idebe (0688 082 089)  
Page 67  
In agriculture  
(a) It is used to kill weeds  
(b) It is used to check cracking in pipes used for irrigation purpose  
(c) It is used to measure the moisture of materials stored in soils  
(d) It is used to measure amount of moisture content stored in grains and control pests  
In transport  
(a) It is used to inspect passenger’s luggage before boarding the plane  
(b) It is used to inspect airline luggage for hidden explosives  
Science Field  
(a) It is important aid to biomedical researchers studying the cellular functions and  
bone formation in mammals  
(b) It is used in research in red blood cell survival studies  
(c) It is used to tell researchers whether oil wells are plugged by sand or not  
(d) It is used in biological research, agriculture, pollution control, and archeology  
(e) It is used to analyze electroplating solutions  
Archaeological field.  
(a) It is used for carbon – dating to determine the age of ancient remains  
Artificial Radioactivity  
Artificial radioactivity is the emission of radiation due to bombardment of small  
and stable nuclei by high energetic particles.  
It is also called induced radioactivity or man – made radioactivity  
In artificial radioactivity, the nucleus must be excited by injection of a neutron  
for radioactivity to start  
How Artificial Radioactivity Occurs?  
•
Artificial radioactivity occurs when an atom is bombed with an accelerator or  
exposing it to slow moving neutrons in a nuclear reactor  
Method of Inducing Radioactivity  
▪
▪
Neutron activation  
Photonuclear reaction  
Neutron Activation  
•
•
Is the process whereby neutron radiation induces radioactivity in materials  
Example: Stable cobalt-59 undergo neutron radiation to emit cobalt-60  
ퟓퟗ  
ퟐퟕ  
ퟔퟎ  
ퟐퟕ  
+
푪풐  
ퟏퟎ풏 →  
푪풐  
Written by Geoffrey M Idebe (0688 082 089)  
Page 68  
Photonuclear Reaction  
•
Is the radioactivity induced by bombarding the target nucleus with high energy  
X-rays or gamma rays  
•
Example: In each of the nucleus reaction listen below what is the atomic  
number, mass number and a name of the particle produced?  
(i) Boron 10퐵  
bombarded with a neutron gives lithium  
73퐿푖 particle  
5
(ii) Aluminium 27퐴푙 bombarded by  
훼
-particle to give silicon 30푆푖 particle  
13  
14  
23  
is bombarded by  
훼
-particle to give aluminium 27퐴푙  
푁푎  
(iii)Sodium  
11  
13  
particle  
(iv)Chlorine 35퐶푙 is bombarded with proton gives Sulphur 35푆 particle  
17  
16  
ANS: (i) Particle is alpha (helium)  
(iii) Atom produced is neutron  
(ii) Atom produced is proton  
(iv) Two electrons are produced  
Application of Artificial Radioactivity  
✓
Neutron activation is one of the most sensitive and accurate methods of trace-  
element analysis  
✓
✓
Neutron activation uses nuclear reactors for nuclear energy generation  
Neutron activation uses nuclear reactors for making nuclear bombs  
Hazards/Effects of Nuclear Reaction  
❖
❖
❖
❖
Skin burning and Redding when exposed in radiation  
Death by killing human body cells  
Cancerous tumors  
Genetic mutation  
Precaution to be taken from hazard  
❖
❖
❖
❖
❖
Limiting the time of exposure  
Increase the distance from the source of radiation  
Using materials such water, concrete or lead to absorb the radiation  
Hold radioactive material by using mechanical tong  
Keep it out of the environment a material containing the radiation source  
Types of Nuclear Reaction  
Nuclear fission  
Nuclear fusion  
Written by Geoffrey M Idebe (0688 082 089)  
Page 69  
Nuclear Fission  
•
Is the process whereby unstable nucleus of an atom split into two or more  
smaller nuclei.  
238  
92  
01푛  
94  
36  
140  
56  
•
Example:  
→
퐾푟  
+
퐵푎 + 2  
푈
NB:  
❖
Nuclear fission of heavy element is a highly exothermic reaction that is why it  
is used as a source of energy in form of heat  
❖
If neutron is bombarded with atom the decay will continue until stable atom  
form, since neutron decreases to finish. This chain is called chain reaction  
Application of Nuclear Fission  
✓
It is used in nuclear power plants to generate electricity  
✓
It is used in making nuclear bombs  
Nuclear Fusion  
•
•
I
s the process whereby lighter nuclei joining together to form heavier nucleus.  
Example:  
Nuclear fusion of deuterium and tritium yield helium, neutron and  
heat energy  
ퟐퟏ푯  
ퟑퟏ푯  
ퟒퟐ푯  
ퟏퟎ풏  
+
→
+
+
energy  
NB:  
❖
❖
❖
❖
Nuclear fusion of heavy element than iron or nickel is endothermic reaction  
Nuclear fusion of lighter element is exothermic reaction  
Nuclear fusion occur naturally in stars  
Nuclear fusion occur artificially in human enterprises  
Application of Nuclear Fusion  
o
o
It is used in nuclear power plants to generate electricity  
It is used in making nuclear bombs. For example, hydrogen bomb  
Carbon – 14 Dating  
•
I
s the scientific method which is used to determine age of dead living and non-  
living organism  
Half-life of Radioactive Nucleus (Decay)  
•
Half-life is the time required for one half of the nuclei present to decay.  
•
•
It is represented by the symbol (  
Each radioactive material has its own half-life  
푡1/2  
)
Written by Geoffrey M Idebe (0688 082 089)  
Page 70  
Activity  
•
Is the rate of disintegration of radioactive material with time  
OR  
•
•
A
ctivity is the number of atoms decayed per unit time  
Activity also is called count rate. SI unit of activity is count rate per second, (c.p.s)  
Mathematically  
= − 휟푵  
풏풖풎풃풆풓 풐풇 풂풕풐풎 풅풆풄풂풚풆풅 (−휟푵)  
푨풄풕풊풗풊풕풚(푨) =  
풕풊풎풆 풕풂풌풆풏(,휟풕)  
휟풕  
NB:  
▪
Negative means as time goes the number of atoms decrease  
▪
Activity is directly proportional to the original number of atoms presents  
Mathematically  
Activity (A)  
∝
Original number of atoms presents (N)  
퐴 ∝ 푁 – removing the proportionality constant  
퐴 = 푘푁  
But: 퐴 = −훥푁  
훥푡  
훥푁  
−
= 푘푁 = 휆푁  
(
푘 = 휆 = Proportionality/decay constant)  
훥푡  
But: Decay constant,  
휆
is given by  
푙푛2  
휆 =  
(Where by ln2 = 0.693)  
푡1/2  
0.693  
0.693  
푎푛푑 푡1  
=
∴ 휆 =  
푡1/2  
λ
2
•
Generally the final amount remaining after time t is given by  
풕
푵
푶
풕ퟏ/ퟐ  
푵 =  
풐풓 푵 = 푵푶  
푶
풏
ퟐ
Where by  
N
NO  
t
=
Final mass/activity/Amount remaining after time t  
Initial (Original) amount/fraction/activity/percentage  
Total time taken/Time taken to decay  
=
=
t1/2  
=Half life  
휆 = Decaying constant  
풏 = 풏풖풎풃풆풓 풐풇 풉풂풍풇 − 풍풊풗풆풔, 풏 =  
풕
풕
ퟏ
ퟐ
Written by Geoffrey M Idebe (0688 082 089)  
Page 71  
The half life of a radioactive element can be calculated by using  
1. Linear method  
•
•
This involves dividing the initial mass/ percentage /fraction by two after each half life  
In general, If No is the initial mass and t1/2 the half life then:  
푵
푶
푵
푵
푵
푶
푶
푶
NO  
ퟒ
ퟖ
ퟏퟔ  
ퟐ
Example: The count rate of a radioactive indium falls from 3200 counts per minute to  
200 counts per minutes in 220 minutes. Determine the half – life of the radioactive isotope  
Soln:  
3200  
1600  
800  
400  
200  
Total number of half lives = 4  
Total time taken  
= 220 minutes  
ퟐퟐퟎ  
=
= ퟓퟓ 풎풊풏풖풕풆풔  
풕ퟏ/ퟐ  
ퟒ
2. Formula method  
•
The formula used is:  
풕
푵
풕
푵
ퟏ
ퟐ
ퟏ/ퟐ  
= ퟐ풏  
푶푹  
푵푶  
푵푶  
−풕  
w
hereby: 풏 =  
(
)
풏 푖푠 푡ℎ푒 푛푢푚푏푒푟 표푓 ℎ푎푙푓 − 푙푖푣푒푠  
풕
ퟏ/ퟐ  
Example: If a radioactive isotope has a half –life of 2.5 hours, how long will it take for  
256 grams of the isotope to decay to 32 grams?  
Soln:  
풕
푵
From:  
= (ퟏ  
풕
ퟏ/ퟐ  
)
ퟐ
푵
푶
풕
풕
ퟑ
= (ퟏퟐ)ퟐ.ퟓ → (ퟏퟐ) = (ퟏퟐ)ퟐ.ퟓ  
ퟑퟐ  
ퟐퟓퟔ  
풕
풃풚 풄풐풎풑풂풓풊풏품 풆풙풑풐풏풆풏풕풔,  
ퟑ =  
→ 풕 = ퟑ 풙ퟐ. ퟓ = ퟕ. ퟓ 풉풐풖풓풔  
ퟐ. ퟓ  
3. Graphical method  
•
This method involves plotting a decay curve, then using the curve to work out  
the half life  
Radioactive Decay Curve  
•
I
s the exponential curve drawn with number of atoms on the vertical axis and  
time for disintegration on the horizontal axis  
(Is a graph of either mass, count rate, activity, percentage e.t.c against time)  
Written by Geoffrey M Idebe (0688 082 089)  
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