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Physical Chemistry

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4 Jan 2007 17:57:20 IST

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1478

atomic structure

None

can you plzz tell me which formula i am supposed to use in this particular question.

find the ratio of radii of hydrogen atom to that of dueterium atom.

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edison

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4 Jan 2007 20:22:18 IST

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use the Bhor's theory of Hydrogen atom acoording to which

Radii of stationaty orbits is given by

r_n = (

₀h²/

m e²) n²/Z meter

= (0.53 x 10^-10) n²/Z

Where Z is no. of protons in the nuclei.

Total no. of neucleons = 2 for deuterium, but Z = 1

and nucleon in hydrogen atom = 1, also Z = 1 for hydrogen atom.

ayush_2711

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5 Jan 2007 17:01:59 IST

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hydrogen and dueterium are isotopes so the value of Z will be same for these two.isn't it?

also can i use the formula of rutherford's model i.e R = 1.33 * 10^-13A^1/3

edison

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5 Jan 2007 21:30:18 IST

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Exactly, I have rectified the same. Thank You very much

ayush_2711

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6 Jan 2007 12:22:01 IST

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but sir,

what's the answer? 1:1 or 1:2

edison

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6 Jan 2007 21:22:43 IST

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The answer should be 1:1.

ayush_2711

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8 Jan 2007 11:22:56 IST

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thankyou.

The_Emperor

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10 Jan 2007 20:15:40 IST

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the answer is not 1:1 as the atomic masses of H and D are not same.(apply rutherfords formulae).if iam wrong then plz correct me.

you_saket

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11 Jan 2007 11:57:57 IST

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can you plzz tell me which formula i am supposed to use in this particular question.

find the ratio of radii of hydrogen atom to that of dueterium atom.

lonelyguy

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22 Jan 2007 00:42:35 IST

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a formulAE IS NOT GOING TO apply there u have to start from the basics as ratio for atm radii in cases of isotopes the one having the more no of nucleons will have the larger radii and in case of same comp but diff E confi as cuin d9 and d10 the confi which is more stable will have the larger radii
if for any further confusions mail me gagar.iitk@gmail.com

drishti_mishra

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22 Jan 2007 17:16:47 IST

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this question's from bahadur(obj.).the answer here is given as 1:1.but i just want to ask one question why can't we use rutherford's formula?it's damn confusing.someone plz... reply!

Titun

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22 Jan 2007 18:13:43 IST

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Hiii,

It's simple.

Remember for the same orbit, all isotopes have the same radius.

So, dueterium and hydrogen have the same radii for the same orbit.

This can also be shown from the formula

So, cheers !!!!!!!!!!!!!!!!!!!!!!!!!!!

drishti_mishra

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23 Jan 2007 17:40:17 IST

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if we use r=1.33*10^-13A^1/3,then we get the answer 1/2

drishti_mishra

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26 Jan 2007 12:06:35 IST

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hi! I would like an expert preferably edison to clarify my doubt.if u want me to send this as a separate question,then let me know.

edison

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26 Jan 2007 12:21:42 IST

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Dear Drishti

I think the formula u are trying to highlight is

R = R_o A^1/3

where R_o = 1.07 x 10^-15 m

and A = mass number of the nucleus = neutrons + protons

But this formula is applicable for RADIUS OF THE NUCLEUS BUT NOT FOR

ATOMIC RADIUS.

drishti_mishra

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27 Jan 2007 13:17:01 IST

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thankyou sir! i've understood my mistake.

Anand Sahay

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26 Mar 2007 01:02:55 IST

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Isotopes don't have equal atomic radii. In the Bohr theory expressions the electronic mass m should be replaced by

the reduced mass.

= M.m/M+m, where M is mass of nucleus and m is mass of electron. For different isotopes

are different, which results in slight differences in the atomic radii of isotopes.If we neglect m with respect to M, the

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