Introduction

The Rutherford model was devised by the New Zealand-born physicist Ernest Rutherford to describe an atom. Rutherford directed the Geiger–Marsden experiment in 1909, which suggested, upon Rutherford's 1911 analysis, that J. J. Thomson's plum pudding model of the atom was incorrect. Rutherfords new model for the atom, based on the experimental results, contained new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with this central volume also containing the bulk of the atomic mass of the atom. This region would be known as the "nucleus" of the atom.

Computer Model Initial Values

mass of helium atom= 4u where u is the unified atomic mass number

mass of gold atom = 197u

charge of helium atom = 2e where e is the electron charge

charge of gold atom = 79e

Forces

Force is calcuated by F = kqQ/r^2 the electrostatic force equation

k = 9.0*0.03 where 0.03 is a factor scaling to scale down/up to fit the x and y dimensions of the computer model, in the nature world k = 9x10^9

q = charge of first particle

Q = charge of second particle

r is the distance that separates the 2 charged particles

Evolution

the ordinary differential equations are

dx[i]/dt = vx[i]

dvx[i]/dt = xForce[i]/m[i]

dy[i]/dt = vy[i]

dvy[i]/dt = yForce[i]/m[i]

where x is the horizontal position of charge particle

i is the array index of all charge particle

t is time

vx is velocity in x direction

xForce is the vector sum of all x-direction forces calculated based on i with all the other [0] to [n] excluding [i] charges particles where n is 80 since it is assume there will be a maximum number of charges of 80.

m is the mass of charged particles

vy is velocity in y direction

yForce is the vector sum of all y-direction forces calculated based on i with all the other [0] to [n] excluding [i] charges particles where n is 80 since it is assume there will be a maximum number of charges of 80.

Auto and Manual Selection of combo-box

auto - automatically randomised the y position of a helium He particle back to the edge of the left screen and shoots in vx as the same initial vx

manual - user can drag on the helium particle to try out their choice of particle y -position and investigate the new trajectory

Rutherford Atom-Model Assumption

The gold atom cannot be moved by fixing the velocity in both x and y idrection as zero all the time.

There is a single particle at the centre of the atom, charge value = 79 u

Rutherford Atom-Model 2 Assumption

The gold atom is made up of 9 individual charge particles that cannot be moved, they are all fixed in their velocities in both x and y idrection to be zero all the time.

There is a group of 9 particles spread out tightly at the centre of the atom, each particle charge is 79u/9. This is a mathematical division as it was too tedious to have 79 particles so to test the model, I just created 9 particles to approximate instead

Thomson Atom-Model configurable Assumption

The gold atom is made up of 9 spread out individual charge particles that can be moved or reposition, they are all fixed in their velocities in both x and y idrection to be zero all the time.

There is a group of 9 particles spread out loosely at the atom, each particle charge is 79u/9. This is a mathematical division as it was too tedious to have 79 particles so to test the model, I just created 9 particles to approximate instead

Thomson Atom-Model configurable each atom Assumption

The gold atom is made up of 79 spread out individual charge particles that can be moved or reposition for exploration and learning, they are all fixed in their velocities in both x and y idrection to be zero all the time.

There is a group of 79 particles spread out loosely at the atom, each particle charge is 79u/79 = 1u. This is the best computer model for Thomsons model of the atom

Experimental basis for Rutherford model

Through conducting inquiry activities on these 4-option computer model, students can obtain computational data (visualise via the histogram or otherwise the He particle trails) and behave like scientists and make conclusion based on evidence rather than from reading texts and looking at static pictures.

Rutherford overturned Thomsons model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny and heavy nucleus. Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure. If Thomson was correct, the beam would go straight through the gold foil. Most of the beams went through the foil, but a few were deflected.

Rutherford presented his own physical model for subatomic structure, as an interpretation for the unexpected experimental results. In it, the atom is made up of a central charge (this is the modern atomic nucleus, though Rutherford did not use the term "nucleus" in his paper) surrounded by a cloud of (presumably) orbiting electrons. In this May 1911 paper, Rutherford only committed himself to a small central region of very high positive or negative charge in the atom.