Which element in Charles Daltons periodic table isn't an element?

Answer 1

Charlie Dalton was not a famous chemist. However his distant cousin John Dalton was. John Dalton did not have a Periodic Table to work with -- he did his work about 70 years too early for that. However, he did have a bit to do with elements and atoms.

The name 'oxygen' means acid-maker. In Dalton's time chemists thought that every acid had to have oxygen in its formula. So he believed that what we now call hydrochloric acid, with formula HCl, contained oxygen in its formula. He therefore described an atom of this substance, which was then known as muriatic acid, as containing one atom each of hydrogen, oxygen, and 'muriatic radicle'. This 'muriatic radicle' was, in effect, an atom of chlorine from which an oxygen atom had been removed. A lot of futile effort was spent trying to remove the oxygen from chlorine gas to obtain this 'element' (but not by John Dalton).