a) The key nding in Rutherford\'s alfa particle scattering experiments was: a) T

Question

a) The key nding in Rutherford's alfa particle scattering experiments was:

a) The incident alfa particles lost kinetic energy equal to the energy di erence between quan-
tized Bohr orbits.
b) A very large percentage of incident alfa particles were scattered through large angles, in-
dicating that positive charge was distributed over the entire volume of the atom.
c) Most incident alfa particles were either unde
ected or scattered through very small angles.
However, a few particles were scattered through angles greater than 90 degrees, indicating a con-
centration of positive charge in an atomic nucleus.
d) Most incident alfa particles were either unde
ected or scattered through very small angles,
indicating that positive charge was distributed over the entire volume of the atom.
e) Most incident alfa particles were either unde
ected or scattered through very small angles,
indicating that atoms were electrically neutral.

b) The Bohr radius of the hydrogen atom is a0 = 0.053nm. Compute the radius of the
n = 6 orbit in singly ionized helium. (Note that the helium atom has two protons in the
nucleus.)

Explanation / Answer

a)
c) Most alpha particles are un deflected or scattered through very small angles. However few particles were scattered through angles greater than 90 degree indicating the concentration of positive charge in an atom
b) The radius of the nth orbit is
rn = n2 a0/ z
Where a0is the Bohr radius and z is the atomic number
The radius of the n = 6 orbit is
r6  = 62 x 0.053 nm / 2
r6 = 18 x 0.053 nm
r6 = 0.954 nm

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