- •
Alpha particles fired at gold foil

- –
Foil thin so alpha particle only scattered once

- –
Evacuated tube used

- –
Zinc Sulfide screen showed scintillations

- –
Alpha source produced a narrow beam to allow precise measurements

- *
Also monoenergetic

- *
- –
Most passed through

- –
Some were scattered

- –
Very few were reflected

- –
Showed that the alpha particle was colliding with a dense, positively charged object, much more massive than \({}^{4}_{2}He\)

- –
Allowed theoretical upper limit on size of gold nuclei to be calculated

- –

At a distance \(d\) from a charge \(Q\), the potential will be given by

\begin{equation} V=\frac{Q}{4\pi\epsilon_{0}d}\nonumber \\ \end{equation}Hence,

\begin{equation} E_{p}=\frac{Q}{4\pi\epsilon_{0}d}q\nonumber \\ \end{equation}Since this can be equated to \(E_{k}\) when the particle is stationary, \(d\) can be found:

\begin{equation} d=\frac{Qq}{4\pi\epsilon_{0}E_{k}}\nonumber \\ \end{equation}- •
Assumes head on collision, which was impossible to detect

- •
Neglects the strong force

- •
Neglects any recoil

However, the result did confirm that the atom is mostly empty space.

- •
Electrons are quantised, and can only exist in given energy levels

- •
Their position is best given by an electron cloud model

- •
Nucleus contains protons and neutrons

- •
\({}^{A}_{Z}X\), where \(A=\) the nucleon number, and \(Z=\) the proton number

- •
Isotopes will have a different number of neutrons

The nucleon expressed as a mass in grams approximates to the mass of one mole of a given isotope.

One mole of a substance contains the same number of entities as there are atoms in 12g of carbon-12; \(6.02\times 10^{23}\).