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Radioactivity- Nuclear reaction

Radioactivity- Nuclear reaction

Nuclear radiation- How was radioactivity discovered ?

The Discovery of Radioactivity

In any chemical reaction atoms can gain, lose, or share electrons, but the identity of the atoms does not change. But nuclear reactions are different. Nuclear chemistry is concerned with the structure of atomic nuclei and the changes they undergo. Whereas chemical reactions involve only small energy changes, nuclear reactions involve much bigger energy changes.

This table offers a comparison between chemical reactions and nuclear reactions

Chemical reactionsNuclear reaction
– Occur when bonds are broken and formed – Occur when nuclei combine, split and emit radiation
– Involve only valence electrons with small energy changes – Can involve protons, neutrons and electrons, associated with large energy changes
– Atoms keep the same identity although they might gain, lose, or share electrons, and form new substances. -Atoms of one element are often converted into atoms of another element.
– Temperature, pressure, concentration, and catalysts affect reaction rates.Temperature pressure and catalysts do not normally affect reaction
Comparison between Chemical and Nuclear reactions

In 1895, German physicist Withelm Roentgen (1845-1923) discover that invisible rays have been emitted when electrons bombarded the surface of materials. These rays induced photographic plates to darken, and Roentgen named these high-energy emissions X-rays. Another French physicist Henri Becquerel (1852-1908) was discovering minerals that deliver light after being exposed to daylight a phenomenon Known as phosphorescence. Building on Roentgen’s work. Becquerel had to determine whether or not phosphorescent minerals also emitted X-rays.

Becquerel discovered that phosphorescent uranium salts produced spontaneous emissions that darkened photographic plates. He observed this phenomenon even when the uranium salts were not exposed to light. Chemist Marie Curie (1867 1934) and her husband Pierre Curie (1859-1906) took Becquerel’s mineral sample and isolated the components emitting the rays. They concluded that the darkening of the photographic plates was due to rays emitted from the uranium atoms present in the mineral sample. Marie Curie named this process: radioactivity, the rays and particles emitted by a radioactive source are called radiation.

Radioactivity- Nuclear reaction

The discovery of radioactivity by Marie and Pierre Curie was really important in developing the nuclear chemistry. In 1898, they identified two new elements, polonium and radium, based on their radioactivity.

Definition of radioactivity and radiation

Radioactivity is the spontaneous breakdown of an atom’s nucleus by the emission of particles and/or radiation. 

Radiation is the emission of energy through space in the form of particles and/or waves.

Types of Radiation

Isotopes are atoms of the same element that have different number of neutrons. Radioisotopes are isotopes of atoms with unstable nuclei. They emit radiation to attain more stable atomic configurations in a process named radioactive decay. During the radioactive decay unstable nuclei release energy by emitting radiation. The three common types of radiation are alpha, beta, and gamma.

Radioactivity- Nuclear reaction
Radioactivity- Nuclear reaction

Ernest Rutherford (1871-1937), who performed the famous gold foil experiment that helped to define modern atomic structure, identified alpha beta, and gamma radiation when studying the effects of an electric field on the emissions from a radioactive source. The effects of an electric field on gamma rays, alpha particles, and beta particles.

Radioactivity- Nuclear reaction

Alfa particles

An alpha particle (α) has the same composition as a helium nucleus: two protons and two neutrons- symbol: “He”.

The charge of an alpha particle is 2+ due to the presence of the two protons. Alpha radiation consists of a stream of alpha particles. Alpha particles are relatively slow moving compared with other types of radiation because of their mass and charge. Thus, alpha particles are not very penetrating, a single sheet of paper stops alpha particles. Polonium-210, an atom whose nucleus contains 84 protons and 126 neutrons, undergoes alpha decay by emitting an alpha particle. Note that the reaction is balanced. That is the sum of the mass numbers (superscripts) and the sum of the atomic numbers (subscripts) on each side of the arrow are equal. The total number of neutrons plus protons does not change in the nuclear process.

Radioactivity- Nuclear reaction

Beta Particles

A beta particle is a very fast-moving electron that is emitted when a neutron in an unstable nucleus converts into a proton. The symbol of beta particles is β or e-. They have a 1- charge. Their mass is so small compared with the mass of nuclei that it can be approximated to zero.

Beta radiation consists of a stream of fast-moving electrons. An example of the beta decay process is the decay of iodine-131 into xenon-131 by beta-particle emission. Note that the mass number of the product nucleus is the same as that of the original nucleus (they are both 131, but its atomic number has increased by 1 instead of 53). This change in atomic number occurs because a neutron is converted into a proton, as shown by the following equation

Radioactivity- Nuclear reaction

Gamma rays

Gama rays are photons which are high-energy electromagnetic radiation. the symbol of these emissions is γ. Because photons have no mass and no Charge the emission of gamma rays does not change the atomic number or mass number of a nucleus. Gamma rays almost always come with alpha and beta radiation, as they account for most of the energy loss that occurs.

For example, gamma rays accompany the alpha-decay reaction of uranium-238.

Summary- Types of radiations

Radioactivity- Nuclear reaction