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Whichelementhas (a) Twoshells , both ofwhich arecompletely filled withelectrons ? (b) the electronicconfiguration2, 8, 2 ? (c) a totalof threeshellswith fourelectronsin thevalenceshell ? (d)a total of twoshells ,withthreeelectronsin the valenceshell (e)twiceas manyelectronsin the second shellas in its firstshell ? |
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Answer» Solution :(a) Sincenoblegases (Group 18) haveall theirshells completely filledwith electronsthereforethe given element must be a noble gas. Since it has twocompleted shell(2,8)it belongsto 2ndperiod. Thus, theelements is neon (Ne). (b) Sinceeach periodbeginswith the filling of anew shell, thereforethe elementhavingelectronicconfiguration2, 8, 2belongsto 3rdperiod. Further, sincethe element has twoelectronsin theoutermostshell,it belongsto group 2. Inother words the given element belongs to group2 of the 3rd period. thusthe element ismagnesium (Mg). (c) Sincethe given element has totalthree energy shells with a total of4 electronsin the VALENCE shelltherefore, the electronicconfigurationof the element is2, 8, 4 , . In otherwordsthe elementbelongstogroup 14 of the3rdperiod. Thus the elementis silicon (Si). (d)Since the givenelement has a total of two energyshellswith threeelectronsin the valence shells therefore theelectronicconfigurationof the elements 2, 3. Inother words theelementbelongstogroup 13 ofthe 2ndperiod.thus theelement is boron(B). (e) Thegiven elementhas twoshells. But in THEFIRST shellsthe maximumof ELECTRONSIS 2. Sincethe NUMBER of theelectrons in the 2ndshell istwicethe electrons in the Istshell ,thereforethe numberofelectronsin the 2ndshell is 4 and thecompleteelectronicconfigurationof the elementis 2, 4. In otherwordsthe givenelementbelongsto GROUP14 of the2ndperiod. Thus the element iscarbon (C). |
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