Thomson

Thomson thought an atom consists of a sphere of positive charge with negatively charged electron embedded in it.

In 1897, Thomson discovered the negatively charged particle in atoms that we call electrons. Experimentally, he showed that electrons have a negative charge and are 1000 times lighter than hydrogen atoms, the atoms with the least mass. Thomson knows atoms are neutral in charge so atoms must also have a positive part.

(This was called the plum and pudding model. A blueberry muffin is like this model. In other words, the bread of the muffin is like the positively charged sphere and the blueberries are like the negatively charged electrons.)

http://socratic.org/chemistry/a-closer-look-at-the-atom/cathode-ray-tube-experiment (Back)