Nuclear Radius Flashcards
What three ways have we estimated the radius of the nucleus?
- Rutherford Scattering Experiment
- Distance of closest approach
- Electron Diffraction
Describe the principles of the Distance of Closest Approach method to estimate the atomic radius
- Fire a positively charged particle of known velocity / energy at a nucleus
- Assume all the Kinetic Energy will be transferred to electric potential energy
- Kinetic = kQq / r
- r is the only unknown and can be solved for, this is an OVERESTIMATE of the atomic radius
Describe the principles of the Electron Diffraction method to estimate the atomic radius
- Electrons are accelerated to high velocities such that they behave like a wave
(DeBroglie’s Wavelength) - Electrons are fired at thin foil of atoms
- Electrons diffract between two nuclei
- Forms concentric rings on curved surface
- Angle of first minimum can be used to calculate atomic radius
When electrons diffract between two nuclei for nuclear radius estimation, what is the “slit separation”
2r, where r is the atomic radius
What equation is used with electron diffraction to estimate nuclear radius
d*Sin(X) = 1.22 * Lambda
(1.22 is the first instance of a minimum when on a curved surface, idk there’s some funny maths behind it)
Describe how Rutherford estimated the nuclear radius using back scattering.
Probability of back scatter for 1 atom thick
= Area Nucleus / Area Atom
P = pi(R.Nucleus)^2 / pi(R.Atom)^2
p^1/2 = R.Nucleus / R.Atom
p^1/2 * R.Atom = R.Nucleus
What Assumptions are made when approximating the density of nuclear matter
- Nucleus is spherical
What is the probability of backscatter in Rutherford’s gold foil experiment
1 in 10,000
Advantages and drawbacks of electron diffraction to estimate nuclear radius
Advantages: Very accurate
Disadvantages: Requires specialised often expensive equipment
Advantages and drawbacks of closest approach to estimate nuclear radius
Advantages: Free, Simple
Disadvantages: Generally always provides an overestimate (inaccurate)
