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| 1. |
On thebasisof quantumnumber, justifythat thesixthperiodof theperiodictableshouldhave 32elements. |
| Answer» Solution :In themodern periodic table , eachperiodstartswith thefillingsof a newprincipal energylevel. Thusthesixthperiodbeginswith thefillingof principalquantumnumber `n=6 ` . Whenn=6,L =0 , 1,2,3 . Butaccordingto aufbauprinciplethe electronsare addedto differentorbitalsin orderof theirincreasingenergies . Now theenergyof 6d- subshellis higherthan thatof 7s- subshellbutenergies of5d-and 4f- subshells arelower thanthat of6d-subshell . Thereforein 6thperiodelectronscan befilledin only 6s- 4f, 5d and6p- subshellswhoseenergiesincreasein THEORDER `: 6 s lt 4f lt5 d lt6 p`Now s- subshells hastwo p-subshell has threed-subshellhas fiveand f- subshellhas sevenorbitals. Hencein allthere are 16 (2+ 3 +5 + 7)orbitalsthat canbe filledin THISPERIOD. Sinceaccordingto pauli's exclusions PRINCIPLE eachorbitalat the maximumcan accommodate two elements therefore16 orbitals at the d maximum can have32electrons and hencesixthperiodhas 32elements. | |