Dipole Moment

comwiz72

Hi, I'm stuck on a certain question in a tutorial sheet, and would appreciate a nudge in the right direction.

The problem is in one particular question to which I missed notes due to illness, and won't have time to copy up before they need handed in.

The question is on dipole moments:

The relative permittivity of xenon at S.T.P. (0C and 1 Atmosphere) is 1.001352. Estimate the magnitude of the dipole moment induced in each xenon atom when the gas is subjected to an electric field E of strength of 5 x 10^5 V/m

Avogadro's Number Na = 6.02 x 10^23
Volume of 1 mole of gas at S.T.P. = 2.24 x 10^-2
Permittivity of vacumn = 8.85 x 10^-12

If the equilibrium inter-nuclear separation r in a completely ionic molecule is 2.8 x 10^-10 metres, calculate its permanent electric dipole moment, and compare with the value obtained above.


Like I said, I don't want the answer or solution, but I'm at a bit of a loss as to where to begin, and would appreciate a little explanation.

I've worked out the internuclear separation of the atoms, and I think I know where to go, but do I need to use the relative permittivity of the xenon to work out the electric field strength within the gas, then use the dipole moment calculation to get the result?

Meir Achuz

You are given E. Use the permittivity to find P (Polarization vector).
Then use P=np, where n is the number density of atoms to find the dipole moment p.

comwiz72

ah of course, using the susceptibility = permittivity - 1
thats what i was looking for, thanks, i just couldn't see it :P