The chemical bonds between atoms in organic molecules are on the order of 10-10

Question

The chemical bonds between atoms in organic molecules are on the order of 10-10 meters in length and 4 electron volts in strength. Suppose you would like to determine the structure of a molecule by imaging the positions of the atoms in the molecule. You could choose to use electro-magnetic waves, an electron microscope, or a beam of neutrons.

(a) Find the energy of photons that would be needed to resolve the inter-atomic separations. Could this energy disrupt the chemical bonds?

(b) Find the energy of electrons that would be needed to resolve the inter-atomic separations. Could this energy disrupt the chemical bonds?

(c) Find the energy of neutrons that would be needed to resolve the inter-atomic separations. Could this energy disrupt the chemical bonds?

Explanation / Answer

(a) Energy of photon = hc / wavelength = 6.625*10^-34 * 3*10^8 / 10^-10*1.6*10^-19 = 12422 eV

     12422 eV > 4 eV (bond energy) hence disruption of bonds will occur.

(b) The momentum of the electron is obtained from:

     p = h/wavelength = 6.625*10^-34 / 10^-10 = 6.625 * 10 ^-24 kg m /s

     Energy T = p2/2m = 6.625 ^2 * 10^-48 / 2*9.1*10^-31*1.6*10^-19 = 150 eV

    150 eV > 4 eV (bond energy) hence disruption of bonds will occur.

(c) The momentum of the neutron is obtained from:

     p = h/wavelength = 6.625*10^-34 / 10^-10 = 6.625 * 10 ^-24 kg m /s

     Energy T = p2/2m = 6.625 ^2 * 10^-48 / 2*1.675*10^-27*1.6*10^-19 = 0.015 eV

     0.015 eV < 4 eV (bond energy) hence no disruption of bonds will occur.

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