Role Of Isotopes In Chemistry
The first three Thorium, radiator, and ionio, of atomic number 90, were identified. Non-radioactive were instead discovered in 1914 by O. Hönigschmid, who found two of the lead. The term was introduced in 1913 by F. Soddy. Isotopes are atoms of the same element that have an equal number of protons but a different number of neutrons. The mass numbers are always indicated with A, while Z refers to the atomic numbers of the elements. The atomic number symbolizes the number of protons in the nucleus of an atom and is used to identify the position of the element on the periodic table. The mass number of an atom is the number of neutrons in its nucleus. The isotopes of the elements have different physical properties due to the variation in their atomic masses. Because of this difference, these isotopes have different densities, as well as melting and boiling points. However, the isotopes of an element always have very similar chemical properties. The similarity occurs because only electrons are used in chemical reactions, not in neutrons or protons.
Features
They can be stable or unstable (or radioactive), natural, i.e. existing in nature, or artificial, i.e. produced as a consequence of provoked nuclear reactions. The electronic structure is identical for all of the same elements; equal is the number of protons that form the nucleus of each. It is the atomic number; the number of neutrons is different (see e.g. in fig.) and therefore the mass number. Usually, it is indicated by proceeding the symbol of the chemical element by two numbers, of which one, at the bottom, is the atomic number, the other, at the top, is the mass number. Thus, the two stable carbons (atomic number 6 and mass number 12 and 13) are indicated by the symbols 126C and 136C, respectively.
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Isotopic Composition And Isotopic Number Of Elements
From a strictly physical point of view, a particularly interesting problem is that the isotopic composition of the elements is extremely varied. While some elements are more stable, others are very poor (e.g., fluorine does not have stability) due to the different stability of the various nuclides (nucleus). A picture of the situation (determined by nuclear forces) is provided by the following rules of thumb: a) the first Mattauch rule says that there are no stable isobars, that is, there is only one stable nuclide if the mass number A is odd; b) Mattauch's second rule says that. if A is even, there are several stable isobars; elements that have only one stable nuclide, i.e. without stable, have odd mass number A and atomic number Z (except 34Be); if Z is even there are numerous (the number of stable nuclides is ≥3); c). Aston's rule, finally, says that if Z is odd, the element has at most stable (i.e. at most two stable nuclides). Based on these rules, it is possible, at least in broad terms, to provide for the constitution in buildings of any element.
Isotopic Separation
To separate various methods of the same element are used, based on the slight differences in chemical and physical properties mentioned above, or, where are reduced to the ion state, based on the different electrical and magnetic behavior deriving from the different specific charges. Among the isotopic separation methods, we will mention the gas phase diffusion, the thermal diffusion, the fractional distillation, the centrifugation, all methods in which are not ionized, as well as electrolysis and electromagnetic separation, in which, instead I am in an ionic state.
Isotopic Effect (Or Displacement)
In spectroscopy, due to the dependence of the frequency of radiation emitted by an atom from the mass of the atom itself, two of the same elements emit in the same transition two slightly different frequencies (the relative difference of the two frequencies is: / = (me / M2) M, where is the electronic mass, M the atomic mass of and M + M that of the other).
Use Of Isotopes
In biology, they are mainly used in investigations on the localization of some chemical compounds in given organs or tissues, or even in particular cells or parts of them, and in the study of the replacement of some chemical constituents of organisms. The technique consists in introducing into the organism, orally or by injection or otherwise, substances containing a certain percentage of one or more radioactive (marked elements); after a certain time, it is possible to proceed with the search and possibly with the measurement of which are found in a given organ or a given substance extracted from an organ. A particular application, very important for various historical and geological problems, is that of the 146C, which has a half-life of 5600 years, for the dating of organic finds.
FAQs on Periodic Table - Isotopes Element
1. What are isotopes and how are they represented in chemistry?
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. Since they have the same number of protons, they share the same atomic number (Z) and occupy the same position on the periodic table. However, their mass number (A), which is the sum of protons and neutrons, is different. They are represented with the mass number as a superscript and the atomic number as a subscript before the element's symbol, like AZX. For example, the isotopes of carbon are written as 12C and 14C.
2. Why do isotopes of an element show similar chemical properties but different physical properties?
The chemical properties of an element are determined by its electron configuration, specifically the number of valence electrons. Since all isotopes of an element have the same number of protons, they also have the same number of electrons to remain electrically neutral. This results in identical chemical behaviour. However, their physical properties, such as density, melting point, and boiling point, depend on atomic mass. As isotopes have different numbers of neutrons, their atomic masses differ, leading to variations in these physical characteristics.
3. How do isotopes explain why the atomic mass of an element on the periodic table is often a decimal value?
The atomic mass displayed on the periodic table is not the mass of a single atom. Instead, it is a weighted average of the masses of all naturally occurring isotopes of that element, calculated based on their relative abundance. For instance, chlorine has two main isotopes: chlorine-35 (~75.77% abundance) and chlorine-37 (~24.23% abundance). The weighted average of these masses results in an atomic mass of approximately 35.5 amu, which is a decimal value.
4. What are some common examples of isotopes for elements like Hydrogen and Carbon as per the NCERT syllabus?
According to the CBSE/NCERT curriculum, key examples of isotopes include:
- Hydrogen: It has three isotopes: Protium (1H, one proton, no neutrons), Deuterium (2H, one proton, one neutron), and Tritium (3H, one proton, two neutrons).
- Carbon: Its main isotopes are Carbon-12 (12C, six protons, six neutrons), which is the most abundant, and Carbon-14 (14C, six protons, eight neutrons), which is radioactive and used in carbon dating.
5. What are some important real-world applications of specific isotopes?
Isotopes have crucial applications across various fields due to their unique properties. Key examples include:
- Carbon-14 (14C): Used in radiocarbon dating to determine the age of ancient organic materials.
- Cobalt-60 (60Co): Emits gamma rays and is used in radiotherapy for cancer treatment and for sterilising medical equipment.
- Uranium-235 (235U): A fissile isotope used as fuel in nuclear power plants to generate electricity.
- Iodine-131 (131I): A radioactive isotope used in medicine to diagnose and treat thyroid disorders.
6. What is the fundamental difference between isotopes and isobars?
The main difference lies in their atomic and mass numbers. Isotopes are atoms of the same element (same atomic number, Z) with a different number of neutrons (different mass number, A). In contrast, isobars are atoms of different elements (different atomic numbers, Z) that happen to have the same mass number (A). For example, 14C and 14N are isobars because they both have a mass number of 14 but belong to different elements, Carbon and Nitrogen.
7. What makes some isotopes stable while others are radioactive?
The stability of an atomic nucleus depends on the neutron-to-proton (n/p) ratio. For lighter elements (Z < 20), a ratio close to 1:1 generally results in a stable nucleus. For heavier elements, a higher ratio is needed for stability. Nuclei with an n/p ratio falling outside the 'band of stability' are unstable. These radioactive isotopes undergo decay, emitting particles or energy to transform into a more stable configuration.
