Atoms are made up of negatively charged electrons orbiting a positively charged nucleus.
Most particles undeflected
Deflected particle
Atoms are of the order of 1010 m in diameter. That’s a mind-boggling one ten- millionth of a millimetre! Amazingly, the nucleus is 100 000 times smaller again, with the electrons being 10 000 times smaller again. Dealing with matter as small as this, it’s truly remarkable that we know as much as we do about the structure of the atom, and we’re still learning.
Rutherford’s Gold Foil Experiment
Fig 22.1: Rutherford’s gold foil experiment
Prior to Ernest Rutherford’s gold foil experiment in 1909, the atom was thought to be made up of a random mixture of electrons and positively charged particles. Electrons had already been discovered and atoms were known to be neutral, so the ‘plum pudding’ model was used to describe how the negative and positive charged particles mixed together just as currants and raisins do in a plum pudding.
DEMONSTRATION 22.1 Demonstration of Rutherford’s Gold Foil Experiment
