What did JJ Thomson discover about atom? What did his atom model look like?

J. J Thomson discovered sub-atomic particle called the electrons.

J. J Thomson's model of the atom looks like a solid sphere

Explanation:

J. J Thomson described the model of the atom as a solid shpere of positive charged, with the negetively charged electrons stack to it. The model of the atom was called Thomson's Plum Pudding Model Of Atom.

The electrons were discovered through his Cathode Ray Tube Experiment in 1897.