问题描述：
ThefollowingquestionsrefertotheBohrmodeloftheatom.
a>Defineanelectronshell;
b>Defineanelectronorbit;
c>Inwhichelectronshellareelectronswiththelowestpossibleenergytobefound?
d>Electronstravelathighspeed.Whatstopsthemfromflyingrightawayfromthenucleus?
e>Howbigisthenucleuscomparedwiththesizeoftheatom?
f>Howheavyisthenucleuscomparedwiththeweightoftheatom?
g>Ifwerideabikequicklyaroundandaroundacirculartrack,weuseupalotofenergy;wegetslowerandsloweraswerunoutofenergyandeventuallystop.Isthiswhatelectronsdotoo?Discuss
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裴伟民回答：
a>
Anelectronshell,alsoknownasamainenergylevel,isagroupofatomicorbitalswiththesamevalueoftheprincipalquantumnumbern.
b>
Anelectronorbitistheregioninwhichanelectronmaybefoundaroundasingleatom.Specifically,electronorbitsarethequantumstatesoftheindividualelectronsintheelectroncloudaroundasingleatom.
c>
shell1
d>
Becauseoftheelectromagneticattractionbetweennucleus(protons)andelectrons
e>
Anatomisabouttenthousandtimeslargerthananucleusinradius.
f>
Anucleusweighsalmostequaltotheatomit'sin.(anucleustakesmorethan99%inweightofaatom)
g>Thebikestopsbecauseoftheresistancecomesfromground&air.Whileinanatom,there'snosuchkindofresistance.Sotheelectronkeepstheircircularflying.
