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General Chemistry

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Radioactivity

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In nuclear reactions, significant changes occur in the composition of the nuclei of the atoms involved. These reactions usually release tremendous amounts of energy. One of the reasons for the nuclear changes can be attributed to the stability of the nucleus.

The formation of nucleus from the subatomic particles - neutrons and protons, results in the release of energy. The mass of these individual particles in the nucleus is greater than that of the actual nucleus that is formed. This loss of mass is due to the change of mass into energy. The energy-mass relation can be represented in terms of the equation:

E = mc2,

where m represents the mass, and c represents the speed of light (3x108 m/s).

If the nucleus of an atom is not stable, it can get transformed into another nucleus. A plot of the number of neutrons versus the number of protons is often used to assess the stability trends of elements. If the number of protons and neutrons are equal, the nucleus is considered to be reasonably stable. As the atomic number increases, the trend changes.

Isotopes of elements having atomic numbers above 83 are unstable atoms. These unstable atoms can undergo disintegrations. The half-lives of some radioactive elements are shown in

Table 1.


When a helium nucleus is formed, there is always some degree of loss of mass. If the loss of mass equals 3.1 x 10–5 kg during the formation of one mol of it, what is the binding energy?

A 3.1 x 10–5 J
B 1.8 x 1019 J
C 9.3 x 103 J
D 2.8 x 1012 J
Ans. D The mass loss can be equated with the binding energy. In essence, mass loss can be calculated using the equation E = mc2.

Energy = (3.1 x 10–5 kg)( 3 x 108 m/s)2 = 2.8 x 1012 kg. m/s2 = 2.8 x 1012 J.

Radioactivity Flashcard List

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In nuclear reactions, significant changes occur in the composition of the nuclei of the atoms involved. These reactions usually release tremendous amounts of energy. One of the reasons for the nuclear changes can be attributed to the stability of the nucleus. The formation of nucleus from the subatomic particles - neutrons and protons, results in the release of energy. The mass of these individual particles in the nucleus is greater than that of the actual nucleus that is formed. This loss of mass is due to the change of mass into energy. The energy-mass relation can be represented in terms of the equation: E = mc2, where m represents the mass, and c represents the speed of light (3x108 m/s). If the nucleus of an atom is not stable, it can get transformed into another nucleus. A plot of the number of neutrons versus the number of protons is often used to assess the stability trends of elements. If the number of protons and neutrons are equal, the nucleus is considered to be reasonably stable. As the atomic number increases, the trend changes. Isotopes of elements having atomic numbers above ≈83 are unstable atoms. These unstable atoms can undergo disintegrations. The half-lives of some radioactive elements are shown in Table 1. All the following are true regarding radioactive rays, except:A α-particles are positively chargedB β-particles are negatively chargedC γ rays are electromagnetic rays and can be deflected by an electric fieldD There are radioactive emissions in which the mass number is not affected
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In nuclear reactions, significant changes occur in the composition of the nuclei of the atoms involved. These reactions usually release tremendous amounts of energy. One of the reasons for the nuclear changes can be attributed to the stability of the nucleus. The formation of nucleus from the subatomic particles - neutrons and protons, results in the release of energy. The mass of these individual particles in the nucleus is greater than that of the actual nucleus that is formed. This loss of mass is due to the change of mass into energy. The energy-mass relation can be represented in terms of the equation: E = mc2, where m represents the mass, and c represents the speed of light (3x108 m/s). If the nucleus of an atom is not stable, it can get transformed into another nucleus. A plot of the number of neutrons versus the number of protons is often used to assess the stability trends of elements. If the number of protons and neutrons are equal, the nucleus is considered to be reasonably stable. As the atomic number increases, the trend changes. Isotopes of elements having atomic numbers above ≈83 are unstable atoms. These unstable atoms can undergo disintegrations. The half-lives of some radioactive elements are shown in Table 1. Which of the following is true regarding radioactivity?A As the atomic number increases, eventually the neutron-proton ratio values become < 1B As the atomic number increases, eventually the neutron-proton ratio values become > 1C As the atomic number increases, eventually the proton-neutron ratio values become > 1D None of the above
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In nuclear reactions, significant changes occur in the composition of the nuclei of the atoms involved. These reactions usually release tremendous amounts of energy. One of the reasons for the nuclear changes can be attributed to the stability of the nucleus. The formation of nucleus from the subatomic particles - neutrons and protons, results in the release of energy. The mass of these individual particles in the nucleus is greater than that of the actual nucleus that is formed. This loss of mass is due to the change of mass into energy. The energy-mass relation can be represented in terms of the equation: E = mc2, where m represents the mass, and c represents the speed of light (3x108 m/s). If the nucleus of an atom is not stable, it can get transformed into another nucleus. A plot of the number of neutrons versus the number of protons is often used to assess the stability trends of elements. If the number of protons and neutrons are equal, the nucleus is considered to be reasonably stable. As the atomic number increases, the trend changes. Isotopes of elements having atomic numbers above ≈83 are unstable atoms. These unstable atoms can undergo disintegrations. The half-lives of some radioactive elements are shown in Table 1. The most probable set of particles that were given off during the series of nuclear changes from 232Th to 224Ra are:A Two alpha particles and one beta particleB One alpha particle and two beta particleC One alpha particle and three beta particlesD Two alpha particles and two beta particles