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| 1. |
How wouldyou justifythe presence of 18elements in the5thperiodof the periodic Table. |
| Answer» SOLUTION :In themodern periodictableeach periodstartswith thefillings of a principal energylevel. Thusthe 5thperiodbeginswith thefillingof principal quantumnumbern=5. Whenn= 5, l = 0, 1,2,3 .Butaccordingto aufbauprincipal , the electronsare addedtodifferentorbitalsin orderof theirincreasingenergies. Nowthe energies of 5d - and5f- subshell. are higher than thatof 6S- subshellbut thefilledonly in5s, 4d- and 5p- subshellswhoseenergies increase intheorder`: 5 s LT 4 d lt 3 t p.` NOWS- subshellhas two , p- subshellhas threeand d-subshellhas five -orbitals. Hencein allthereare 9 (1+3+5)orbitalsthat can have 2 electrons therefore9 orbitals at themaximumcan have18 electrons andhence5thperiodhas18 elements | |