Magic numbers......
these helps u to find whether a nucleus is radioactive or not...
Just as electrons arev present in diff shells around the nucleus , similarly it has been postulated that the nucleons are present in diff. shells within the nucleus wich have different energies...the nuclei containing same no. of protons and eutrons but whose energies differ are called nuclear isomers
It is observed that those nuclei are extra stable and have large no. of isotopes whose nuclear shells are fully filled i.e have closed shells.....these are those wich contains 2, 8 , 20 , 50 , 82 , or 126 neutrons or prtons....these are thus called magic numbers of nucleus shell
eg.
4He2 , no. of protons = 2 , no. of neutrons = 2
wen both the number of protons and neutrons are magic numbers , the nucleus is very stable , this is y most of the radioactive elements disintegrate to form a stable isotope of lead bcoz in lead , both neutrons are protons are magic numbers
okk lets take a qs
4He2 , 39Ca20 , 210At85 , wich of the foll will be radioactive?????
1) He , prtons = 2 , neutrons = 2
both are magic numbers so its stable , so non radioactive
2)Ca , prtons = 20(magic no.) but neutrons = 19 (odd no.).....as it has protons in magic no. but n/p ratio is < 1 , so it is expected to b radioactive
3)At it is radioactive as there is no stable nuclei after atomic no. 83
P.S---> THESE magic no.s are nt that similar to 2,8,8,18,18 32
that thing is diff. its diff....
hope it helped u , post ur comments :) :)
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