Which scientist described an atom made of a solid positively charged substance with electrons dispersed throughout it?

The scientist who described an atom as consisting of a solid positively charged substance with electrons dispersed throughout it is J.J. Thomson. This model, known as the "plum pudding model," was proposed in 1904. Thomson's idea was based on his discoveries regarding the electron and the overall charge of the atom. He envisioned the atom as a sphere of positively charged matter in which electrons were embedded, similar to raisins in a pudding. This model was later replaced by the more accurate Rutherford model, which introduced the concept of a nucleus at the center of the atom. However, Thomson’s plum pudding model was a significant step in the understanding of atomic structure.