So let's go back for a status report around the end of the 19th century. So what did we know towards the end of the 19th century? The atom is electrically neutral. The negative charge is carried by electrons. We knew that there was some carrier of negative charge. We knew further that this electron is very, very tiny. Small mass. And so if it has a very small mass, then by difference, then the bulk of the mass of atom must be contained in the positive charge.
So now the question is, what is the spatial distribution of charge inside an atom? You might say, well why do we want to know that? Well, we're trying to get a physical
model of the atom so that then we can start to address the question of chemical reactivity. So we have got to know where all the players are before we can attribute action to them. So let's now take a look at models of the atom.
For the first modern model of the atom we go to J. J. Thompson. J. J. Thompson, he was a professor of physics and director of the Cavendish lab at Cambridge University. The other Cambridge. Cambridge University. And this Cavendish Lab was named after Henry Cavendish. The same one who is credited with the discovery of hydrogen in 1766. He never married, and when he died he bequeathed this fortune to Cambridge University, and they took that money and established a physics laboratory, which is still in operation to this day