1 Thomson's atomic model (1897)

• After discovering the electron, J.
• J.
• Thomson proposed that the atom is a solid (not hollow), homogeneous sphere of uniform positive charge, with negative electrons embedded in it like seeds in a watermelon (the "plum pudding" picture).
• The total negative charge of the electrons equals the positive charge of the sphere, so the atom as a whole is electrically neutral.

Features:

• the positive charge is spread evenly through the whole volume of the atom;
• the electrons are scattered inside the positive sphere;
• the atom is solid, with no empty space.

• Thomson's model could explain neutrality but gave no explanation of how the positive charge and the mass were arranged.
• An experiment with alpha particles tested it and showed it to be wrong.