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Concept of Iso-Series (In Hindi)
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In this lesson we will learn about iso-series mainly isotopes, isobars, isotones etc with suitable examples and problems for IIT-JEE students

Niranjay Kumar Dwivedi
(N.K.D.Sir) is a Complete Chemistry faculty for IIT~JEE, and NEET examination. with more then 8 year of Teaching experience

U
thank you sir! gramin arthvywatha n economical survey pe bhi video provide kre !

2. Isotopes They were discovered by F. Soddy. They are atoms of a given element which have the same atomic number but differ in the their mass numbers. Thus isotopes have the same nuclear charge but differ in the number of neutrons in the nucleus. Isotopes have identical chemical properties but differ in physical properties. They possess different charge : mass ratio, i.e., e/m of isotopes are different and they can be separated on this basis. The instrument which separates the particles according to their charge: mass ratio is called Mass sepectometer. Examples 2 3 (i) Hydrogen (Protium) Heavy hydrogen (Deuterium) Tritium (p 1, e , n 2) (p 1, e 1, n O) (ii) 8016, 8017, 8017, 8018, (iii) I-CI35, 1C37 (p-1, e 1, n 1) 66 , (6

3. Elements have non-integral atomic masses due to the existence of isotopes. The atomic weight of an element is the average of weights of all the isotopes of that element. For example, the fractional atomic weight of chlorine (35.5) is due to the existence of isotopes 17CI and 17CI in the ratio of 3 1. Their average atomic weight is the atomic weight of chlorine. Average weight Weight of 3 atoms of i,CI+ Weignt or one atom Total four atoms 3x35 +1x37 105+37 142 4 4 4 = 35.5 amu.

4. Kinetic Isotopic Effect The effect on the rate of a reaction (kinetics of a reaction) due to the presence of an isotope of an element, is called kinetic isotopic effect, for example: During electrolysis of water (H20) containing heavy water (D20) the H-O bond in H20 breaks up at a faster rate than D-O bond in D2O. As a result we get heavy water. Thus, the manufacture of heavy water by the electrolysis of ordinary water is a beautiful example of kinetic isotopic effect Isobars They are atoms with the same MASS NUMBER but different ATOMIC NUMBERS. Thus isobars have different number of electrons, protons and neutrons but the sum of neutrons and protons in their nucleus is the same. Examples : 1 H and-He', l8Ar", 19K" and 20 ", 52Te o, 56Ba' "and 54Xe As isobars are the atoms of different elements they possess different physical and chemical properties. In the periodic table, isobars are placed in separate groups

5. Isotones (Isoneutronic species) They are the atoms possessing the same number of neutrons but different mass numbers Oxygen 140 (p-8; n-8) Nitrogen 'N p7; n-8) Carbon 4C (p-6; n-8) Isosters These are the species with same number of atoms with equal number of electrons and similar bonding0-C-o and N-N

6. Isoelectronic pair among the following is (a) Ca and K (c) K and Ca 2-+ An isobar of 20Ca40 is (b) Ar and Ca2+ (d) Ar and K (b) 2o Ca38 (d) i8 Ar38 18 Ar 40 (c) 20Ca42 The electronic configuration of a dipositive ion M2+ is 8. 14 and its mass number is 56. The number of neutrons present is (a) 32 (c) 30 The nucleus of an atom contains (a) proton and electron (b) neutron and electron (c) proton and neutron (d) proton, neutron and electron (b) 42 (d) 34

7. Which of the following make up an isotonic triad ? 31 Ja r, 19 20 233 U, 290 Th. 2 1 2 (c) Pu The number of electrons and neutrons of an element is 18 and 20 respectively. Its mass number is (b) 17 (d) 38 (c) 37 Which one of the following ions is not isoelectronic with O-? (a) Ti* (c) F (b) Na* (d) N