According to J.J. Thomson, an atom consists of a positively charged sphere. Which subatomic particles are embedded in it?

According to J.J. Thomson, an atom consists of a positively charged sphere and the electrons are embedded in it. He compared the model of an atom to a Christmas pudding where electrons, in a sphere of positive charge, were like currants (dry fruits) in a spherical Christmas pudding. Thomson’s model explained that atoms are electrically neutral as the negative and positive charges are equal in magnitude.