Title SP-5_Ch-28_Nuclei.pdf ✅

100 Nuclei NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Isobars Nuclei having the same mass number A but different nuclear charge (Ze) are called isobars. Examples : (1) 11Na22 and 10Ne22 are isobars with the same mass number 22. (2) 11Na24 and 12Mg24 are isobars with the same mass number 24. Isobars are atoms of different elements and hence they have different chemical properties. Isotones Nuclides having the same number of neutrons are called isotones. For example 17Cl37 and 19K39 are isotones with 20 neutrons. Nuclide : A single nuclear species with specific values of both Z and N is called a nuclide. Example 1 : A nucleus has atomic number 11 and mass number 24. State the number of electrons, protons and neutrons in the nucleus. Solution : The number of electrons in nucleus = 0, electrons do not exist in the nucleus Here Z = 11, A = 24 Number of protons in nucleus (Z) = 11 Number of neutrons in nucleus (N) = A – Z = 24 – 11 = 13 Example 2 : Select the pairs of isotones from the following nuclei. 12Mg24, 1H3, 2He4, 11Na23 Solution : (i) 1H3 and 2He4 Number of neutrons = 3 – 1 or 4 – 2 = 2 (ii) 12Mg24 and 11Na23 Number of neutrons = 24 – 12 or 23 – 11 = 12 Example 3 : Write the names and formulae of the three isotopes of hydrogen. Solution : Protium (1H1), Deuterium (1H2), Tritium (1H3). Example 4 : The three stable isotopes of neon Ne20, Ne21 and Ne22 have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u respectively. Obtain the average atomic mass of neon. Solution : Average atomic mass of neon. Aneon = 11 2 2 3 3 12 3     x A xA xA xx x = 90.51 19.99 0.27 20.99 9.22 21.99 100    = 1809.29 5.67 202.75 20.184 100   