Question

State the reason why Rutherford's Model of the atom failed to describe the observed behaviour of matter

can u add pictures and words

Answer 1

Here’s why the electron can’t go around the nucleus whereas planets can go around the sun:

“Electrons are charged particles. Charged particles that are accelerating, produce electromagnetic waves (radiation). Electromagnetic waves carry energy. Therefore, an accelerating charged particle gives off energy”

How are electrons accelerating?

“Acceleration” is defined as “change in velocity with time”. Velocity is a vector quantity that includes both how fast something is moving (For ex. a car going at 100 Km/Hr.) and in what “direction” it’s moving. (This is the definition of vector quantities. They have both a magnitude and direction)

An electron going around the nucleus is accelerating because its direction of motion is constantly changing with time, since it is moving in a circle.

Why do accelerating charges give off electromagnetic waves?

You will have to read Electrodynamics to understand that. But its a fact that they do.

How can we show EM waves carry energy?

You’ll have to read Electrodynamics for that too. But its a fact that they do carry energy.

Conclusion: Since the electron is continuously losing energy as shown above, its speed around the nucleus cannot remain constant (if it did, the kinetic energy would remain constant, which is not possible as it is losing energy). So the speed must go down and consequently, the radius of its rotation will have to go down (this has to do with centripetal acceleration). And hence the speed will keep reducing as the electron keeps giving off energy by emitting EM waves and the radius of its rotation will keep decreasing and it will soon crash into the nucleus. If it crashed into the nucleus, atoms wouldn’t exist and you and I wouldn’t exist. But we do, hence Rutherford’s model is wrong and electrons don’t move like planets around the sun.

Planets don’t crash into the sun because they don’t give off any significant energy.