Subatomic particles alpha

X-rays, or gamma rays generated by nuclear decay. Ionizing radiation also includes several types of subatomic particles, such as beta radiation (high-energy electrons) and alpha radiation (helium ions) and others. Medical X-rays are an example of a common beneficial exposure to ionizing radiation. Nuclear radiation is used to generate electricity and cure disease, but is also an important element in military weapons. Uses of nuclear radiation pose serious issues of human exposure and environmental contamination. 

Thus it was the physicists who took the next steps toward understanding the nature of matter. In 1896 the French physicist Henri Becquerel discovered radioactivity, and in 1897 the English physicist J. J. Thomson discovered the first subatomic particle, the electron. Subsequently, studies of the radiation emitted by radioactive atoms showed that these atoms emitted radiation of three different kinds, which were called alpha, beta, and gamma after the first three letters... 

The atom was once thought to be the smallest unit of matter, but was then found to be composed of electrons, protons, and neutrons. The question arises are electrons, protons, and neutrons made of still smaller particles In the same way that Rutherford was able to deduce the atomic nucleus by bombarding atoms with alpha particles (Chapter 3), evidence for the existence of many other subatomic particles has been obtained by bombarding the atom with highly energetic radiation.This research over the past centmy has evolved into what is known as the "standard model of fundamental particles, which places all constituents of matter within one of two categories quarks and leptons. 

The experimenters set up a lead-shielded box containing radioactive polonium, which emitted a beam of positively charged subatomic particles through a small hole. Today, we know that the particles of the beam consisted of clusters containing two protons and two neutrons and are called alpha particles. The sheet of gold foil was surrounded by a screen coated with zinc sulfide, which glows when struck by the positively charged particles of the beam. 

Figure 12-1. Tb shows the sensor head from the Mars rover missions of 2(K)4. The head contains a curium-244 source that emits X-rays and 5.81 MeV alpha particles. The X-rays cause fluorescence in Martian rock samples, and the alpha particles stimulate X-ray emission as well. X-ray emission stimulated by bombardment by alpha and other subatomic particles such as protons is called punicle induced X-ru emission, or I lXE. llie X-ray detector is a new room-temperature type, which in the low temperature of the Martian night (below 4U°C.) exhibits low noise and high signal-to noise ratio for excellent resolution and sensitivity. Note the concentric design of the sensor head with six (im-244 sources arranged around the central detector. The X-ray spectrum of Figure 12-14 was acquired with the sensor head.

Alpha Particles are subatomic particles made up of two neutrons and two protons ejected from the nucleus of an unstable atom. These particles are not able to penetrate most materials-even a piece of paper or the outer layer of human skin can block an alpha particle. However, when alpha-emitting un.stable atoms are inhaled, alpha particles become panicularly dangerous because they will kill lung cells, which could lead to scarring and po.ssible cancer. Gamma radiation is a packet of energy, sometimes called a photon, that is emitted from the nucleus of an unstable atom. 

Radioactive nuclides contain atoms that disintegrate by emission of subatomic particles and gamma or X-ray photons. In alpha decay, a helium nucleus of 2 protons and 2 neutrons is emitted and reduces the mass number by 4 and the atomic number by 2. In beta decay, an electron - produced by the disintegration of a neutron into a proton, an electron, and an antineutrino - is emitted from the nucleus and increases the atomic number by 1 without changing the mass number. Sometimes a positron together with a neutrino is emitted. And sometimes an electron may be captured from the K (outermost) sheh of the atom the resultant electron hole in the K shell is filled by electrons from outer orbits and causes the emission of X-rays. Alpha and beta decay generally leave the resultant daughter nuclei in an... 

Physicists found that an alpha particle made up of four subatomic particles, rather than six, would fit their theories beautifully. The proton-neutron structure has been accepted ever since. 

In the outer regions of the atom are the negatively charged electrons, which are too light to interpose an important barrier to the passage of the alpha particles. Although the protons and alpha particles are as massive as atoms, they are actually bare atomic nuclei. They take up so little room in comparison with the atom that they, too, despite their large mass, may be considered subatomic particles. 

Meanwhile, Soddy had gone on to describe the exact manner in which an atom changed as it gave off subatomic particles. If an atom lost an alpha... 

Certain elements are radioactive because their nuclei are unstable and spontaneously decay through the ejection (or capture) of subatomic particles, often accompanied by the emission of high-energy electromagnetic radiation. The principal radioactive decay processes are alpha decay, beta decay, gamma emission, and spontaneous fission. 

Before 1934, the study of radioactivity was limited to reactions of the relatively few radioisotopes found in nature. In that year, Irene and Frederic Joliot-Curie, French physical chemists, found that radioactivity could be induced in nonradioactive nuclei by bombarding them with small, subatomic particles. They produced an artificial radioactive isotope, nitrogen-13, by bombarding boron-10 with alpha particles from a natural radioisotope ... 

As the name suggested this type of radiation consists of subatomic or groups of subatomic particles. Three sorts are recognised alpha, beta and neutrons. These and gamma radiation are termed ionising radiation. 

Uranium has two major isotopes, (99.3 %) and (0.7 %). is relatively plentiful and stable, while is scarce and radioactive. Radioactive isotopes are susceptible to, and often spontaneously undergo, fission. During fission, the nucleus of an atom splits, several smaller atoms are produced, and energy and subatomic particles (gamma radiation, neutrons, alpha, and beta particles predominantly) are released. In addition to spontaneous fission, fission can also be induced when the... 

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