# List of Radioactive Elements

URL: https://sciencestruck.com/chemistry/list-of-radioactive-elements
Category: Chemistry
Published: 2009-09-11T00:55:00
Updated: 2009-09-11T00:55:00
A radioactive element is one 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 ScienceStruck article has a list of radioactive elements that abound in nature, arranged in the order of increasing atomic number, along with their decay modes.

Let us 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.

### 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.

### 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 these 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 it’s 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 and 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

### Alpha Decay

Nucleus emits a helium nucleus (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. In some cases, double beta decay may occur, involving the emission of two beta particles.

### Gamma Decay

Gamma decay just changes the energy level of the nucleus.

### Electron Capture

One of the rarest decay modes is electron capture. In this phenomenon, an electron is captured or absorbed by a proton rich nucleus. This leads to the conversion of a proton into a neutron in the nucleus, along with release of an electron neutrino. This leads to a decrease in atomic number (transmuting the element in the process), while leaving the atomic mass number unchanged.  
  
A radioactive element may have more than one decay mode.  

### 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, 6C14 and 6C12. 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 relics possible.

### Half-Life of a Radioactive Element

Half-life is the amount of time required, for half quantity of radioactive element to decay. For example C14has a half life of 5730 years. That is, if you take 1 gm of C14, then half of it will have been decayed in 5730 years. In the list presented below, half-lives of all the radioactive elements are presented.

### Radioactive Elements List

Here is a detailed and comprehensive list of natural 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\-)

12.32 years

Beryllium (Be)

4

7

Electron Capture (ε), Gamma Decay)

53.12 Days

Beryllium (Be)

4

8

Alpha

7 x 10\-17sec

Beryllium (Be)

4

10

Beta Decay (β\-)

1,360,000 years

Carbon (C)

6

14

Beta Decay (β\-)

5,730 years

Calcium (Ca)

20

41

Electron Capture (ε)

103,000 years

Calcium(Ca)

20

46

Double Beta Decay (β\-β\-)

\> 2.8 x 1015 years

Calcium(Ca)

20

48

Double Beta Decay (β\-β\-)

\> 4 x 1019

Iron (Fe)

26

54

Double Electron Capture (ε)

\> 3.1 x 1022years

Iron (Fe) (Synthetic)

26

55

Electron Capture (ε)

2.73 years

Iron (Fe) (Synthetic)

26

59

Beta Decay (β\-)

44.503 days

Iron (Fe) (Synthetic)

26

60

Beta Decay (β\-)

2,600,000 years

Cobalt (Co) (Synthetic)

27

56

Electron Capture (ε)

77.27 days

Cobalt (Co) (Synthetic)

27

57

Electron Capture (ε)

271.79 days

Cobalt (Co) (Synthetic)

27

58

Electron Capture (ε)

70.86 days

Cobalt (Co) (Synthetic)

27

60

Beta Decay (β\-), Double Gamma

5.2714 years

Nickel (Ni)

28

59

Electron Capture (ε)

76,000 years

Nickel (Ni) (Synthetic)

28

63

Beta Decay (β\-)

100.1 years

Zinc (Zn) (Synthetic)

30

65

Electron Capture (ε), Gamma

243.8 days

Zinc (Zn) (Synthetic)

30

72

Beta Decay (β\-)

46.5 hours

Selenium (Se)

34

79

Beta Decay (β\-)

3.27 x 105years

Selenium (Se)

34

82

Double Beta Decay (β\- β\-)

1.08 x 1020years

Krypton (Kr)

36

85

Beta Decay (β\-)

10.756 years

Rubidium (Rb)

37

87

Beta Decay (β\-)

4.88 x 1010 years

Strontium (Sr)

38

89

Electron Capture (ε), Beta Decay (β\-)

50.52 days

Strontium (Sr)

38

90

Beta Decay (β\-)

28.9 years

Yttrium (Y)

39

90

Beta Decay (β\-), Gamma

2.67 days

Yttrium (Y)

39

91

Beta Decay (β\-), Gamma

58.5 days

Zirconium (Zr)

40

93

Beta Decay (β\-)

1.53 x 106years

Zirconium (Zr)

40

94

Double Beta Decay (β\-)

\> 1.1 x 1017years

Zirconium (Zr)

40

96

Double Beta Decay (β\-)

2 x 1019years

Niobium (Nb) (Metastable)

41

93

Beta Decay (β\-),Gamma

16.13 years

Niobium (Nb)

41

95

Beta Decay (β\-), Gamma

34.991 days

Molybdenum (Mo)

42

93

Electron Capture (ε)

4 x 103years

Technetium (Tc)

43

99

Beta Decay (β\-)

2.111 x 105years

Ruthenium (Ru)

44

103

Beta Decay (β\-), Gamma

39.26 days

Ruthenium(Ru)

44

106

Beta Decay (β\-)

373.59 days

Palladium (Pd)

46

107

Beta Decay (β\-), Gamma

6.5 million years

Silver (Ag)

47

111

Beta Decay (β\-), Gamma

7.45 days

Tin (Sn)

50

126

Beta Decay (β\-)

2.3 x 105years

Antimony (Sb)

51

125

Beta Decay (β\-)

2.7582 years

Tellurium (Te)

52

127

Beta  
Decay (β\-), Gamma

9.35 hours

Tellurium (Te)

52

129

Beta Decay (β\-)

69.6 minutes

Iodine (I)

53

123

Electron Capture (ε), Gamma

13 hours

Iodine (I)

53

129

Beta Decay (β\-)

15.7 million years

Iodine (I)

53

131

Beta Decay (β\-), Gamma

8.02070 days

Xenon (Xe)

54

125

Electron Capture (ε)

16.9 hours

Xenon (Xe)

54

127

Electron Capture (ε)

36.345 days

Xenon (Xe)

54

133

Beta Decay (β\-)

5.247 days

Cesium (Cs)

55

134

Electron Capture (ε), Beta Decay (β\-)

2.0648 years

Cesium (Cs)

55

135

Beta Decay (β\-)

2.3 million years

Cesium (Cs)

55

137

Beta Decay (β\-), Gamma

30.17 years

Cerium (Ce)

58

144

Beta Decay (β\-)

285 days

Promethium (Pm)

61

147

Beta Decay (β\-), Gamma

2.6234 years

Europium (Eu)

63

154

Beta Decay (β\-), Beta Decay (β+), Gamma

16 years

Europium (Eu)

63

155

Beta Decay (β\-)

2 years

Iridium (Ir) (Synthetic)

77

188

Electron Capture (ε)

1.73 days

Iridium (Ir) (Synthetic)

77

189

Electron Capture (ε)

13.2 days

Iridium (Ir) (Synthetic)

77

190

Electron Capture (ε)

11.8 days

Iridium (Ir) (Synthetic)

77

192

Beta Decay (β\-), Electron Capture (ε)

73.827 days

Iridium (Ir) (Synthetic, Metastable)

77

192

Gamma Decay

241 years

Iridium (Ir) (Synthetic)

77

193

Gamma Decay

10.5 days

Iridium (Ir) (Synthetic)

77

194

Beta Decay (β\-)

19.3 hours

Iridium (Ir) (Synthetic, Metastable)

77

194

Gamma Decay

171 days

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

234

Beta Decay (β\-)

6.75 hours

Uranium (U)

92

233

Alpha

159,200 years

Uranium (U)

92

234

Alpha

245,500 years

Uranium (U)

92

235

Alpha

7.038 x 108 years

Uranium (U)

92

236

Alpha

2.342 x 107 years

Uranium (U)

92

238

Alpha

4.468 billion years

Neptunium (Np) (Synthetic)

93

237

Alpha

2.144 million years

Plutonium (Pu)

94

238

Alpha

87.74 years

Plutonium (Pu)

94

239

Alpha

2.41 x 104years

Plutonium (Pu)

94

240

Alpha

6.5 x 103years

Plutonium (Pu)

94

241

Beta Decay (β\-)

14 years

Plutonium (Pu)

94

242

Alpha

3.73 x 105years

Plutonium (Pu)

94

244

Alpha

8.08 x 107years

Americium (Am)

95

241

Alpha

432.2 years

Americium (Am) (Metastable)

95

242

Alpha, Gamma

141 years

Americium (Am)

95

243

Alpha

7,370 years

Curium (Cm)

96

242

Alpha

160 days

Curium (Cm)

96

243

Alpha

29.1 years

Curium (Cm)

96

244

Alpha

18.1 years

Curium (Cm)

96

247

Alpha

15.6 million years

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 problems. Now, it’s for us to decide, how we intend to use the power of technology placed in our hands.