JEE advanced preparation for Radioactivity

This article will help you in JEE advanced preparation for Radioactivity.

Nucleid Table


A nuclide table is a graphic representation of all known nuclides, whether natural or artificial, stable or radioactive.

All the nuclides were grouped in tables that are the representation on a Cartesian axis of Z = f (N). Thus, each pair of Z-N values uniquely represents a nucleid occupying in these tables a locker.Some authors identify their properties with different colors. For example, in the table presented below, the identification is as follows:

– the color black represents stable nuclides

– mustard color indicates alpha decay

– green indicates positive ß decay or electronic capture

– the light blue color indicates negative ß decay

– pink indicates spontaneous fission

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However, in the graphic representation of Karlsruhe the identification of colors changes. It is not necessary to memorize this data, they are simply references that allow us to better understand this information ordered and presented as a table.

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Nucleides can be classified as isotopes, isotopes, isomers, isotones or isodiaphors.


(from the Greek “same place” …)

They are the nuclides that have the same atomic number (number of protons in the nucleus), but different mass numbers (sum of the number of neutrons and protons in the nucleus). The different isotopes of an element differ, then, in the number of neutrons. They are the same chemical element, that is, they are in the same place in the periodic table. Examples of isotopes are carbon (a) and lithium (b).

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If the relationship between the number of protons and neutrons in an isotope is not appropriate to obtain nuclear stability, the isotope is radioactive and is called a radioisotope. These can be natural and / or artificial and without distinguishing their origin they emit energy and / or particles when they look for the most stable form.

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(from the Greek “just as heavy” …)

When two different nuclides have different number of protons, that is, different atomic number but identical mass number, they are called isóbaros. Examples of isobaros are 40Ca and 40K.

Note that in the case of the isobars, the chemical species changes since the amount of protons that make up the nucleus changes. The number of protons by which one exceeds the other coincides with that of deficit neutrons, so that the sum of nucleons is the same.

Ionizing and non-ionizing radiation

There are two types of radiation: ionizing radiation and non-ionizing radiation.

Ionizing radiation has so much energy that destroys the electrons of atoms, a process known as ionization. Ionizing radiation can affect atoms in living things, so it poses a health risk by damaging the tissue and DNA of genes. Ionizing radiation comes from X-ray machines, cosmic particles from outer space and radioactive elements. Radioactive elements emit ionizing radiation when the atoms decay radioactively.

Non-ionizing radiation has enough energy to displace the atoms of a molecule or make them vibrate, but it is not enough to eliminate electrons from atoms. Examples of this type of radiation are radio waves, visible light and microwaves.

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Electromagnetic spectrum

The radiation energy shown in the spectrum below increases from left to right with frequency intensification.

Types of ionizing radiation

Alpha particles

Alpha (α) particles have a positive charge and are composed of two protons and two neutrons in the nucleus of the atom. Alpha particles come from the decay of heavier radioactive elements, such as uranium, radium and polonium. While alpha particles have a lot of energy, they are so heavy that they deplete their energy over short distances and cannot get too far from the atom.

The health effect of exposure to alpha particles depends largely on the way the person is exposed. Alpha particles lack the energy to penetrate even the outer layer of the skin, so that exposure on the outside of the body is not a major concern. However, inside the body can be very harmful. If alpha-ray emitters are inhaled, ingested or entered into the body through a cut, alpha particles can damage sensitive living tissue. The way these large and heavy particles cause damage makes them more dangerous than those of other types of radiation. The ionizations they produce are very close: they can release all the energy in a few cells. This results in more serious damage to cells and DNA.

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Beta particles

Beta (β) particles are small, fast particles with a negative electrical charge that are emitted from the nucleus of an atom during radioactive decay. These particles are emitted by certain unstable atoms such as hydrogen 3 (tritium), carbon 14 and strontium 90.

Beta particles are more penetrating than alpha particles, but less harmful to living tissue and DNA because the ionizations they produce are more spaced. They travel greater distances in the air than alpha particles but can be stopped by a layer of clothing or a thin layer of a substance such as aluminum. Some beta particles are able to penetrate the skin and cause damage such as skin burns, for example. However, as with alpha emitters, beta emitters are more dangerous when inhaled or ingested.

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Gamma rays

Gamma rays (γ) are weightless packages of energy called photons. Unlike alpha and beta particles, which have energy and mass, gamma rays are pure energy. Gamma rays are similar to visible light but have much higher energy. Gamma rays are usually emitted along with alpha or beta particles during radioactive decay.

Gamma rays constitute a radiation hazard for the entire body. They can easily penetrate the barriers that stop alpha and beta particles, such as skin and clothing. Gamma rays have so much penetration power that it would take several inches of a dense material, such as lead or even a few feet of cement, to stop them. Gamma rays can completely cross the human body; on passing they can cause ionizations that damage tissues and DNA.

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Because of their use in medicine, almost everyone knows X-rays. X-rays are similar to gamma rays in the sense that they are photons of pure energy. X-rays and gamma rays have the same basic properties but come from different parts of the atom. X-rays are emitted by processes external to the nucleus, but gamma rays originate inside the nucleus. They usually have less energy and, therefore, are less penetrating than gamma rays. X-rays can be produced naturally or through electric machines.

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