The noble gases (Helium, Neon, Argon etc.) were not discovered until much later ... Unfortunately for Meyer, his work wasn’t published until 1870, a year after Mendeleev’s periodic table had been ...

neon and xenon (1898). It was debated whether the 'inert' monoatomic gases belonged to the periodic table owing to their lack of 'chemical properties'; elements coming late to the party ...