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In 1910 Rutherford (pictured right) and his co-workers carried out an experiment in which thin sheets of gold foil were bombarded with alpha particles - Leaving Cert Chemistry - Question a - 2007
Question a
In 1910 Rutherford (pictured right) and his co-workers carried out an experiment in which thin sheets of gold foil were bombarded with alpha particles. The observati... show full transcript
Worked Solution & Example Answer:In 1910 Rutherford (pictured right) and his co-workers carried out an experiment in which thin sheets of gold foil were bombarded with alpha particles - Leaving Cert Chemistry - Question a - 2007
Step 1
Describe the model of atomic structure which existed immediately prior to this experiment.
Answer
Prior to Rutherford's experiment, the prevailing model of atomic structure was J.J. Thomson's plum pudding model. This model proposed that atoms were composed of a positively charged 'soup' with negatively charged electrons (like raisins in pudding) embedded randomly within it. The overall charge of the atom was neutral due to the balancing of the positive and negative charges.
Step 2
State these other observations and explain how each helped Rutherford deduce that the atom has a nucleus.
Answer
First observation: Deflection of alpha particles.
Second observation: Alpha particles reflected (bounced back) after colliding with the gold foil.
The deflection of alpha particles indicated that they were experiencing a force strong enough to alter their path as they passed through the gold foil. This suggested that a small, dense, positively charged area existed within the atom, leading to the conclusion that the atom contains a nucleus. The reflection of some alpha particles reinforced this idea, as it implied that a significant mass and charge was concentrated in a tiny region, which could only be the nucleus.
Step 3