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Physical Chemistry

Blazing goIITian

Joined:	24 Dec 2006
Post:	1312

8 Jan 2008 12:46:07 IST

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431

Simple Nuclear Eating My Brain !!

None

these are a list of my doubts plz solve them asap :

1.which is correct:

1.alpha particles are positively charged material particles

2.b are negative waves

3.gamma are neutral in nature

4.b are not electrons

ans : 1

2.what are these magic numbers ? i didnt get the funda !

3.an isotop decays to the extent of 10% in unit time.......t1/2 is ?

ans : 6.93 units

4.late discovery of neutron is attributed to its : neutral nature or high unstability ?

5.neutrino is ejected due to emission of ?

6.how to determine whether a given element is of 4n or whatever series.....such as bismuth.......how to tell which series it belongs to

7.a radioactive element decays by 2 parallel emissions of constants K1 and K2....effective decay constant will be ? (plz dun temme using logic plz temme using mathematical approach)

8.when the conc of a radioactive substance is 0.2 M......and lambda = 10^-2 units...what is the half life time

9.which is correct :a.isotopes are always radioactive b. a rays are negative c.gamma are deflected in magnetic field d.b are negative

10.for higher stability packing fraction is +ve or -ve ? please explain

and most important one :

11.if the ratio of radium n uranium in a sample is 1: 2.8 x 10^6 and t1/2 of radium is 1626 years determine the t1/2 of uranium

PLZ SOLVE ASAP HOWMUCHEVER U CAN.......ILL BE VERY THANKFUL TO U..GOOD REPLIES WILL BE RATED

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Comments (2)

Rasheeda Abbas

Blazing goIITian

Joined: 11 Oct 2007

Posts: 417

8 Jan 2008 13:00:10 IST

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When all the protons or neutrons in a nucleus are in filled shells, the number of protons or neutrons is called a "magic number." Some of the magic numbers are 2, 8, 20, 28, 50, 82, and 126. For example, ¹¹⁶Sn has a magic number of protons (50) and ⁵⁴Fe has a magic number of neutrons (28). Some nuclei, for example ⁴⁰Ca and ²⁰⁸Pb, have magic numbers of both protons and neutrons; these nuclei have exceptional stability and are called "doubly magic."

Madmax

Blazing goIITian

Joined: 24 Dec 2007

Posts: 1111

8 Jan 2008 17:41:43 IST

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1)alpha particles are positively charged material particles (they are doubly ionised He atoms i.e. atoms with protons but no e- So a) is rite
2)Magic numbers are self explanatory ..They are simply Highly stable setups of protons or neutrons
For more read http://www.lbl.gov/abc/wallchart/chapters/06/1.html
3) is little lenghty I'll explain later!!
4)Neutral nature---e- and proton were discovered becos of their electrical properties but neutron can't be found out this way....Just think....How would you detect something as tiny as a neutron with such little mass without knowing any of its properties??
5)Electron neutrinos are generated whenever protons change into neutrons.These are the two forms of beta decay!!
6)By heart the Periodic table

I guess....No Idea Sorry!!
7)Simply K1+K2.....Coz it decays to one product with K1 and to second product at K2 So overall decaying is at K1+K2
Understand this and just put it into the Chemical kinetics rate eqn (Its a 1st order eqn )
8)I din't get the question!!
9)All isotopes are not radioactive but

particles are electrons so -ve So d)
10)Packing Fraction is the quotient of the algebraic difference between the isotopic mass and the mass number of a nuclide, divided by its mass number, often interpreted as a measure of stability.It is ratio between mass defect and mass number.Negative PF means isotopic mass is less than mass number.Here,some mass is transformed to energy as per E=mc^2.Therefore such nuclei are stable.
11) Is long ....i'll post later!!

Just one tip dude

Don't post such bunches of questions ....i think you'll get better answers if you post seperate posts!!

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