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Let us look into the concept of isotones. All matter is made up of atoms in different arrangements. Atoms are made up of protons, neutrons and electrons. Every proton has a positive charge, every electron has a negative charge and every neutron is neutral. It is an important concept in nuclear physics. It is an indispensable part of both physics and chemistry. The meaning of isotones is much more clearly explained with the help of several examples in this unit.
Definition of Isotones
Isotones can be defined as two or more nuclei of atoms consisting of the same number of neutrons. In simple words, atoms with the same number of neutrons but different protons are termed isotones. Therefore, we see two conditions for an atom or nuclei to be termed an isotone. Number one is that the atom or nuclei should have the same number of neutrons. Number two is that they should have different numbers of protons. Atoms in isotones may have different atomic numbers and different atomic masses.
Elements of isotones
Neutrons: Neutrons were discovered in May 1932 by the English physicist James Chadwick. He asserted that neutrons are a new fundamental particle devoid of any charge. It means that these particles lack both positive charges and negative charges. They are neutral in charge, so he named them neutrons.
From the conservation of momentum and energy, he derived the mass of neutrons. He also noticed that the mass of a neutron is very close to the mass of a proton.
MN = 1.00866 amu
1 amu = 1.6749 × 10-27 kg.
The discovery of neutrons led to a better understanding of atomic number (the number of protons and electrons) and atomic mass (the total number of neutrons and protons). The number of neutrons in an atom or nuclei is represented by N.
Protons: Protons were discovered in 1886 by Eugen Goldstein. The word proton means first in Greek. Ernest Rutherford gave this name in 1920 to the hydrogen nucleus. A proton is a subatomic particle having a positive charge. The positive charge of a proton is equal in magnitude to a unit of electron charge. The mass of a proton is equal to 1.67262 × 10-27 kg. One or more protons are present in the nucleus of every atom or nuclei. They form an important part of the nucleus and are represented by the symbol p or p+. They play an important role in the identification of atomic numbers.
Meaning of isotones
The word isotone means “same stretching”. It was derived by the German physicist K. Guggenheimer. He formed the term by changing the p in isotope, meaning proton, to n in isotone, meaning neutron. This means that isotones have a similar number of neutrons and isotopes have similar numbers of protons. Neutron number is represented by a capital N.
Two nuclides will be considered isotones if they have the same neutron number but different proton numbers, whereas nuclides refer to a distinct kind of nucleus or atom having a specific number of neutrons and protons. Nuclides are also termed as nuclear species. They are characterized by the number of neutrons, the number of protons and the energy state of the nucleus. It is characterized by the mass number (represented by A) and the atomic number (represented by Z).
Examples of isotones
Isotones are atoms having a similar number of neutrons and different protons.
Boron-12 and carbon-13 are isotones as both have 7 neutrons
Sulphur-36, chlorine-37, argon-38, potassium-39 and calcium-40 are all isotones of 20 because they have 20 neutrons
Hydrogen-2 and helium-3 are isotones of neutron 1
Beryllium-9 and boron-10 are isotones of neutron 5
Carbon-13 and nitrogen-14 are isotones of neutron 7
Krypton-86, yttrium-89, zirconium-90, molybdenum-92 and radium-88 are isotones of neutron 50.
Uses of isotones
When scientists study numerous nucleic varieties, it is useful to look at nuclei with the same number of neutrons, but altering the number of protons changes the chemical nature of the nucleus. Isotones are used for different purposes. They are used in nuclear power plants. They are also used to form nuclear bombs.
Some of the applications of isotones are
Isotones can be found in various neutron applications. A typical example is the production of technetium-99 used in medical imaging, which is produced by neutron radiation of molybdenum-98 targets. Isotopes that lead to higher cross-sections produce more products and therefore are more efficient.
Another application is in the production of fissionable material for nuclear weapons. This can be done by exposing a heavy isotope. Usually, uranium-235 or plutonium-239 to fast neutrons via bombardment with deuterons accelerated in a particle accelerator or cyclotron. The resulting compound nucleus emits more neutrons on average than it absorbs, increasing the chance of successful fission.
In addition to its use in military applications, isotones can be used as neutron absorbers for reactor control. Generally, reactivity increases when the void (i.e., unfilled) fraction of a reactor’s core is reduced; however, too few neutrons will be absorbed to maintain a chain reaction. Isotones that cannot absorb a neutron or only with a long delay will thus reduce reactivity.
Isotones also play an important role in research reactors. Again, these are used to control power levels using absorbers that will not interfere with the neutron flux by absorbing neutrons or decaying into undesirable isotopes.
Conclusion
In this section, we have understood several things about isotones, along with the definition of isotones, the meaning of isotones and examples of isotones. We learned that they play an important role in nuclear physics. The number of neutrons and protons characterizes them.
According to the definition, if the number of protons in an atom is different and the number of neutrons is the same, it will be termed as isotones. There are several applications and uses of isotones in the field of physics. Apart from this, it also plays an important role in chemistry. Several terms cannot be defined without isotones. They are used in hospitals for medical imaging and also in the production of nuclear weapons.
