In 1871 noble gases wee unknown.
Dmitri Mendeleev.
In 1869 when D. Mendeleev designed his periodic table any element in the period 7 was known. Today francium is in the group 1, period 7, atomic number 87.
I think it he some old guy who does not want anyone too know who he is
It is in 101st element in the Periodic Table.. Md-Mendelevium
Dmitri Mendeleev, although he did it differently we than it is right now. He pridected elements, and now, they've been discovered. Some people discovered elements Mendeleev didn't predict. Most of them were radioactive, like rutherfordium. (Of course, that element was synthetic. There are only 92 natural elements.) Mendeleev used different symbols than we do now, e.g. yttrium was Yt. The elements Mendeleev predicted were gallium, germanium, and scandium.
I think that was Dmitri Mendeleev way back in 1869.
I think
i think argon is solid
i think it was aman
I suppose that you think to periodic table of Mendeleev.
I don't think there is a biological need to inhale argon, and the element has been linked to asphyxiation, but if one were to desire to do so, it would be because argon exists as a gas at room temperature, as the melting and boiling point are -189.35 Celsius and -185.85 Celcius, respectively.
You think probable to gallium.