Therefore isotopes contain same number of protons and electrons The difference

Therefore isotopes contain same number of protons and

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Therefore, isotopes contain same number of protons and electrons. The difference in their masses is due to the different number of neutrons contained in the nuclei, e.g. hydrogen exists in 3 isotopic forms as given below: (i) Ordinary hydrogen whose atomic mass = 1 (ii) Deuterium hydrogen whose atomic mass = 2 (iii) Tritium hydrogen whose atomic mass = 3 All the three isotopes of hydrogen contain 1 proton and 1 electron, but different numbers of neutrons. The ordinary hydrogen atom does not contain any neutron, the deuterium atom also has 1 neutron in its nucleus and the tritium atom also has 2 neutrons in the nucleus. ISOBARS Atoms of elements having different atomic number but the same mass number are called isobars. Since isobars possess different atomic numbers, they must contain different number of protons and electrons in their atoms. Because their mass is the same, the total number of protons and neutrons in each of their nuclei is also the same. For example, argon (atomic number 18) and calcium (atomic number 20) possess same atomic mass, i.e., 40. Argon has 18 electrons, 18 protons and 22 neutrons in its atom. Calcium has 20 protons and 20 neutrons in its atom.
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~ Page 6 of 79 ~ POLYMORPHISM Existence of substance into more than one crystalline forms is known as "POLYMORPHISM". In other words, under different conditions of temperature and pressure, a substance can form more than one type of crystals. This phenomenon is called polymorphism and different crystalline forms are known as ‘polymorphics’. Example of polymorphics are given below: 1. Mercuric iodide (HgI 2 ) forms two types of crystals. (a) Orthorhombic (b) Trigonal 2. Calcium carbonate (CaCO 3 ) exists in two types of crystalline forms. (a) Orthorhombic (Aragonite) (b) Trigonal Polymorphous substances have similar chemical properties but different physical properties. ALLOTROPY Existence of an element into more than one physical form is known as “ALLOTROPY". Under different conditions of temperature and pressure an element can exist in more than one physical forms. This phenomenon is known as allotropy and different forms are known as “allotropes”. An example of allotropes of an element is given below: Coal, lamp black, coke, diamond, graphite, etc. are all allotropic forms of carbon. Allotropy or allotropism (from Greek (allos) , meaning "other", and (tropos) , meaning "manner, form") is the property of some chemical elements to exist in two or more different forms, in the same physical state , known as allotropes of these elements. Also, allotropes are different structural modifications of an element; [1] the atoms of the element are bonded together in a different manner. For example, the allotropes of carbon include diamond (where the carbon atoms are bonded together in a tetrahedral lattice arrangement), graphite (where the carbon atoms are bonded together in sheets of a hexagonal lattice ), graphene (single sheets of graphite), and fullerenes (where the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations).
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