List of Radioactive Elements
A radioactive element is an element with an unstable nucleus, which radiates alpha, beta or gamma radiation and gets converted to a stable element. This article has a comprehensive list of radioactive elements and their properties.This article is your comprehensive reference on radioactivity and radioactive elements.
Radioactive elements abound in nature. This article has a list of radioactive elements which are arranged in the order of increasing atomic number along with their decay modes. Before we have a look at the radioactive elements list, let us understand what do we mean by a radioactive element first! That is, we must understand the phenomenon of radioactivity.
Radioactivity
arrived on the scene of world physics in the 19th century, just when people thought they knew everything in physics! With its discovery in 1896, radioactivity opened up a Pandora’s box of questions and revealed a new world, waiting to be explored in the microcosm of the atomic nucleus.
Let us understand radioactivity and how it led to developments which culminated into the invention of nuclear energy and nuclear bomb! We will also get introduced to certain terms like isotopes and ideas like half life, which will help us understand radioactivity better. Then we will make a list of radioactive elements and study their individual properties.
What is Radioactivity?
Radioactivity is a very interesting phenomenon in nature. Classical Electromagnetism cannot explain radioactivity. It’s a spontaneous and random phenomenon whereby nuclei of certain chemical elements like Uranium, radiate gamma rays (high frequency electromagnetic radiation), beta particles (electrons or positrons) and alpha particles (Helium Nuclei).
By the emission of these particles and radiation, the unstable nucleus gets converted into a stabler nucleus. This is called radioactive decay. In the list of radioactive elements, all the elements which undergo decay are listed. Find more information on radioactivity through the articles, ‘ What is radioactivity?’ and meaning of radioactivity decay.
The Term ‘Radioactive’ – A Misnomer
A radioactive element is a fundamental element whose atomic nuclei demonstrates the phenomenon of radioactivity. The name ‘radioactive’ may suggest to you that radioactive elements radiate radio waves, but unfortunately that is not so! The name ‘radioactivity’ is a misnomer because the radioactive elements have nothing to do with radio waves! The reason is that energy and frequency of a gamma ray which is emitted by a radioactive element, is far beyond that of the radio band of electromagnetic spectrum! So, we are just stuck up with the name!
What Makes an Element Radioactive?
To understand radioactivity, we need to explore the structure of an atomic nucleus. Every nucleus contains neutrons as well as protons. Neutrons are neither positively charged, nor negatively charged, they are neutral particles. Protons are positively charged. As you might remember from high school physics, like charges repel each other while unlike charges attract each other. In the nucleus, protons and neutrons are cramped together in a really very small space.
The protons in the nucleus, all being positively charged, repel each other! So if all the protons repel each other, how does the nucleus stay glued together and remain stable? It is because of the ‘Nuclear Force’.
This force is more stronger than the electromagnetic force, but the range of this force is only limited to size of the nucleus, unlike electromagnetic force whose range is infinite! This nuclear force acts between the protons and neutrons, irrespective of the charge and its always strongly attractive! However, it has limitations of range! So, in the nucleus, there is a constant tussle between the repelling electromagnetic coulomb force of protons and the attractive strong nuclear force.
In a nucleus like Uranium, which has almost 92 protons, coulomb repulsive force becomes too much for the nuclear force to contain. Subsequently, the nucleus is very unstable and radioactive decay occurs, while Uranium decays into a more stable element. Such an unstable nucleus like Uranium, when gently tapped by a neutron, splits up into two other nuclei through nuclear fission, releasing tremendous amount of energy in the process! This is the principle on which nuclear energy and nuclear weapons are based!
The radioactive elements listed below shows all the decay modes of Uranium. A full explanation of radioactivity can only be given, if we plunge deep into quantum physics and elementary particle physics!
Types of Radioactive Decay
This decay may occur in any of the following three ways:
- Alpha Decay: Nucleus emits a helium nuclei (called an Alpha Particle) and gets converted to another nucleus with atomic number lesser by 2 and atomic weight lesser by 4.
- Beta Decay: Beta decay could be of two types. Either through emission of an electron or positron (the antiparticle of electron). Electron emission causes an increase in the atomic number by 1, while positron emission causes a decrease in the atomic number by 1.
- Gamma Decay: Gamma decay just changes the energy level of the nucleus.
A radioactive element may have more than one decay mode. The list of radioactive elements below will give the decay modes of all radioactive elements.
Radioactive Isotopes
When two nuclei have the same atomic number, but different atomic weight or mass numbers, then they are said to be isotopes! Isotopes have the same chemical properties but different physical properties! For example, carbon has two isotopes,
6
C 14 and
6
C 12. Both have the same atomic number, but different number of neutrons. The one with the two extra neutrons is radioactive and undergoes radioactive decay.
The radioactive isotope of carbon was used to develop carbon dating tool, which has made the dating of various elements possible! In the radioactive elements’ list below, all the radioactive isotopes of elements are presented.
Half Life of a Radioactive Element Another term that you need to understand, if you want to understand radioactivity is ‘Half Life’. Those of you from a chemistry background might have heard about half life in nuclear chemistry
. Half life is the amount of time required, for half quantity of radioactive element to decay! For example C 14 has a half life of 5730 years. That is, if you take 1 gm of C 14, then half of it will have been decayed in 5730 years! In the list of radioactive elements below, half lives of all the radioactive elements are presented.
Radioactive Elements List
Here is a detailed and comprehensive list of radioactive elements along with their atomic and mass numbers, decay modes and half lives. Here ‘Beta Decay (β -)’ denotes Electron emission while Beta Decay (β +) denotes Positron emission.
Radioactive Element
Atomic Number
Atomic Mass Number
Decay Type
Half Life
Hydrogen (H)
1
3
Beta Decay (β -)
12 years
Beryllium (Be)
4
10
Beta Decay (β -)
2,700,000 years
Carbon
(C)
6
14
Beta Decay (β -)
5,770 years
Calcium
(Ca)
20
41
Beta Decay (β +)
100,000 years
Iron
(Fe)
26
59
Beta Decay (β -)
45 days
Cobalt
(Co)
27
60
Beta Decay (β -), Gamma
5 years
Nickel
(Ni)
28
59
Beta Decay (β +)
80,000 years
Zinc
(Zn)
30
65
Beta Decay (β -), Gamma
145 days
Selenium
(Se)
34
79
Beta Decay (β -)
70,000 years
Krypton (Kr)
36
85
Beta Decay (β -), Gamma
10 years
Krypton (Kr)
36
90
Beta Decay (β -), Gamma
33 seconds
Rubidium (Rb)
37
87
Beta Decay (β -)
47 billion years
Strontium (Sr)
38
89
Beta Decay (β -)
53 days
Strontium (Sr)
38
90
Beta Decay (β -)
28 years
Yttrium (Y)
39
90
Beta Decay (β -), Gamma
64 hrs
Yttrium (Y)
39
91
Beta Decay (β -)
58 days
Zirconium (Zr)
40
93
Beta Decay (β -)
950,000 years
Zirconium (Zr)
40
95
Beta Decay (β -)
65 days
Niobium (Nb)
41
93
Gamma
4 years
Niobium (Nb)
41
95
Beta Decay (β -), Gamma
35 days
Molybdenum (Mo)
42
93
Beta Decay (β +)
10,000 years
Technetium (Tc)
43
99
Beta Decay (β -), Gamma
210,000 years
Ruthenium (Ru)
44
103
Beta Decay (β -)
40 days
Ruthenium(Ru)
44
106
Beta Decay (β -)
1 year
Palladium (Pd)
46
107
Beta Decay (β -), Gamma
7 million years
Silver
(Ag)
47
110
Beta Decay (β -), Gamma
249 days
Tin (Sn)
50
126
Beta Decay (β -)
100,000 years
Antimony (Sb)
51
125
Beta Decay (β -)
2 years
Tellurium (Te)
52
127
Beta Decay (β -), Gamma
105 days
Tellurium (Te)
52
129
Beta Decay (β -)
67 minutes
Iodine
(I)
53
129
Beta Decay (β -), Gamma
17.2 million years
Iodine (I)
53
131
Beta Decay (β -), Gamma
8 days
Iodine (I)
53
134
Beta Decay (β -), Gamma
52 minutes
Xenon (Xe)
54
133
Beta Decay (β -), Gamma
5 days
Xenon (Xe)
54
137
Beta Decay (β -), Gamma
4 minutes
Xenon (Xe)
54
138
Beta Decay (β -), Gamma
14 minutes
Cesium (Cs)
55
134
Beta Decay (β -), Gamma
2 years
Cesium (Cs)
55
135
Beta Decay (β -), Gamma
2 million years
Cesium (Cs)
55
137
Beta Decay (β -), Gamma
30 years
Cerium (Ce)
58
144
Beta Decay (β -)
285 days
Promethium (Pm)
61
147
Beta Decay (β -), Gamma
2 years
Europium (Eu)
63
154
Beta Decay (β -), Beta Decay (β +), Gamma
16 years
Europium (Eu)
63
155
Beta Decay (β -)
2 years
Lead
(Pb)
82
210
Beta Decay (β -), Alpha
21 years
Bismuth (Bi)
83
210
Alpha
3 million years
Polonium (Po)
84
210
Alpha
138 days
Radon (Rn)
86
220
Alpha, Beta Decay (β +)
1 min
Radon (Rn)
86
222
Alpha
4 days
Radium (Ra)
88
224
Alpha
4 days
Radium (Ra)
88
225
Beta Decay (β -)
15 days
Radium (Ra)
88
226
Alpha
1,622 years
Thorium (Th)
90
228
Alpha
2 years
Thorium (Th)
90
229
Alpha
7,340 years
Thorium (Th)
90
230
Alpha
80,000 years
Thorium (Th)
90
232
Alpha
14 years
Thorium (Th)
90
234
Beta Decay (β -)
24 days
Proactinium (Pa)
91
226
Alpha, Beta Decay (β +)
2 minutes
Uranium (U)
92
233
Alpha
162,000 years
Uranium (U)
92
234
Alpha
248,000 years
Uranium (U)
92
235
Alpha
713 million years
Uranium (U)
92
236
Alpha
23.9 million years
Uranium (U)
92
238
Alpha
4.51 billion years
Neptunium (Np)
93
237
Alpha
2.2 million years
Plutonium (Pu)
94
236
Alpha
285 years
Plutonium (Pu)
94
238
Alpha
86 years
Plutonium (Pu)
94
239
Alpha
24,390 years
Plutonium (Pu)
94
240
Alpha
6,580 years
Plutonium (Pu)
94
241
Beta Decay (β -), Alpha
13 years
Plutonium (Pu)
94
242
Alpha
379,000 years
Plutonium (Pu)
94
243
Alpha
5 years
Plutonium (Pu)
94
244
Alpha
76 million years
Americium (Am)
95
241
Alpha
458 years
Americium (Am)
95
242
Beta Decay (β -), Beta Decay (β +), Alpha, Gamma
16 hours
Americium (Am)
95
243
Alpha
7,950 years
Curium (Cm)
96
242
Alpha
163 days
Curium (Cm)
96
243
Alpha
35 years
Curium (Cm)
96
244
Alpha
18 years
Curium (Cm)
96
247
Alpha
40 million years
Hope this comprehensive list of radioactive elements will be useful to you. These radioactive isotopes have a lot of applications today, ranging from medicine to atomic energy. Since these radioactive elements are harmful, burning up radioactive waste or disposing it, is difficult. Every development in science and technology brings in new developments and problems. Now, it’s for us to decide, how we want to use the power of technology placed in our hands.
