List of 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, 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 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 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 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.