how isotopes and isobars do not obey the law of Definite proportion
Answers
More About Isobars
Atoms of chemical elements having same atomic mass but a different atomic number are called Isobars. The sum of the number of protons and neutrons together form the atomic mass. Therefore, we can also say the number of nucleons present in the nucleus is equal to the atomic mass of an atom. It will have the same number of nucleons.
The number of protons and neutrons alone will vary but the number of nucleons or the sum of protons and neutrons in isobars will always be same. Isobars always have different atomic structure because of the difference in atomic numbers. The number of neutrons makes up the difference in the number of nucleons. Therefore, they are always different chemical elements having same atomic masses. Thus, isobar has different chemical properties.
Learn the concept of an Atomic number here.
By now we know that the atomic masses in isobars are same. Therefore, they have similar physical properties. For example, the isobars iron and nickel. Iron and nickel have atomic number 26 and 28 respectively. However, the mass number is 58.
Another example is argon and calcium with atomic number 18 and 20, respectively. However, they have the same atomic mass 40. Furthermore, sometimes there are series of an element that has same atomic mass. For example, Cobalt (Co), Nickel (Ni), Copper (Cu), and Iron (Fe) have same atomic mass 64 but the atomic number varies.
Examples
18Ar40 19K40 20Ca40
32 Ce76, 34Se76
11Na24 12Mg24
26Fe58, 27 Ni58
27Co64 28Ni64
Quick summary with stories
Isobars, Isotones and Isodiaphers
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Browse more Topics under Structure Of Atom
Introduction: Structure of Atom
Atomic Number
Bohr’s Model of Atom
Charged Particles in Matter
Isotopes
Mass Number
Neutrons
Rutherford’s Model of an Atom
Thomson’s Model of an Atom
Valency
How are Electrons Distributed in Different Orbits (Shells)?
Sub-Atomic Particles
Atomic Models
Shapes of Atomic Orbitals
Energies of Orbitals
Quantum Numbers
Development Leading to Bohr’s Model of Atom
Emission and Absorption Spectra
Towards Quantum Mechanical Model of Atom
Difference between Isotopes and Isobars
Isotope Isobar
Isotopes are atomic structures of same elements having a different mass number/atomic mass Isobars are different chemical elements having same atomic mass.
Atomic numbers of all isotopic forms of a single element are equal. Atomic numbers of isobars vary from each other
They are the same chemical element but their forms are different They are different elements altogether.
All isotopic forms of single elements have different physical properties. Physical properties can be similar to each other
Conclusion
Isotope and isobar indicate the relationships between chemical elements. Therefore, it is necessary to understand the difference between them. Isotopes provide the relationship of different forms of the single chemical element. Isobars indicate the relationship between different chemical elements but having the same atomic mass and thus the same physical properties.