Question

How was it shown that an atom has empty space?

Answer 1

Rutherford alpha scattering experiment is used to explain the empty space in atoms. In this experiment gold foil is used and beams of alpha particles get incident on gold foil and some theoretical calculations were done regarding the atom and its properties and also came to know about the nature of atoms.

Complete answer:
Geiger and Marsden performed an experiment on the scattering of alpha particles; a beam of high energy alpha particles was made to fall on a thin gold foil. The whole arrangement is kept in vacuum so that alpha particles will not collide with the air molecules present there in the atmosphere. The alpha particles while passing through gold foil were deflected in different directions with different angles. Following observation were recorded from experiment:-
1.Most of the alpha particles almost passed straight through gold foil without being deflected
2.Some alpha particles were deflected at small angles since the alpha particle is positive in nature and if it is deflected then something is there in the atom of gold foil which is positive charge because of that deflection occurs.
3. Very few alpha particles were scattered with angles greater than${{90}^{0}}$.
4. Very very few alpha particles bounce back along the same path.
From these points it is concluded that: - All positive charge in the atom is concentrated at the centre in an extremely small space. This space is called nucleus and radius of this nucleus is of the order of ${{10}^{-14}}m$ while radius of atom is of the order of ${{10}^{-10}}m$. Thus radius of the nucleus is only one-thousandth part of the radius of the atom .So the rest of the space in the atom is shown as empty space because most of the particles pass the gold foil without any effect.
So we can get a conclusion that in this way some space is empty in the atom.

Note:
In Rutherford Experiment we have taken gold foil because a thin gold foil ensures that alpha particles were deflected by single collision. Firstly Gold foil was taken because gold can be beaten to convert it into a very thin foil and secondly gold nucleus being heavy produces a large deflection in alpha particles.