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Atom
,→Nuclear Model of the Atom
: [[Ernest Rutherford|Rutherford's]] students [[Ernest Marsden]] and [[Hans Geiger]] fired [[Alpha Particle|alpha particle]]s, which are positively charged, at a very thin sheet of [[Gold]] foil to observe how the [[Alpha Particle|alpha particles]] changed direction as they went through the foil. This was known as [[Rutherford's Alpha Scattering Experiment]].
: They discovered that most of the [[Alpha Particle|alpha particle]]s went through in a straight line. A significant number were [[deflect]]ed and a very small number bounced off the [[Gold]] back towards the [[Alpha Particle|alpha]] source.
: If the [[Plum Pudding Model]] were correct then nearly all of the [[Alpha Particle|alpha particles]] should have passed straight through, unaffected, since the [[Alpha Particle|alpha particle]] is positively charged wile while [[atom]]s should have an even spread of [[charge]]d [[particle]]s all the way through them. There should have been no [[Electrostatic Force|electrostatic force]] to change their direction.
: This showed that the [[atom]] must be mostly empty space, that most of the [[mass]] of an [[atom]] is concentrated in the centre and that the centre is positively charged. This gave [[Ernest Rutherford|Rutherford]] [[Scientific Evidence|evidence]] to develop a new model of the [[atom]] which he proposed in 1911 called the [[Nuclear Model]] in which a very small positively charged [[Atomic Nucleus|nucleus]] is surrounded by [[orbit]]ing [[electron]]s.