The findings of henri becquerel and the curies to discredit what notion held for a very long time?
1.that matter can never be created or destroyed.
2.matter is made up of any smaller parts.
3.matter is radioactive and decays over time.
4.that matter is invisible and indestructible.

Henri Becquerel is considered as father of radio activity. He was the first one who experimentally demonstrated the radioactivity and the nature of particles i.e alpha particle,beta particle and gamma particle.

Madam curie assisted by her husband invented  various artificial radio active elements like radium.

Radio activity is the process of disintegration of a  unstable nucleus into various other nuclei with release of radioactive radiations.

Hence out of four options only option 3 is correct which tells that matter is radioactive and decays over time.

The options 1 ,2 and 4 are the direct consequences of Dalton's law.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.