In his book The Gases of the Atmosphere (1896), Ramsay showed that the positions of helium and argon in the periodic table of elements indicated that at least three more noble gases might exist.
Dalam bukunya The Gases of the Atmosphere (1896), Ramsay menunjukkan bahwa posisi helium dan argon dalam tabel periodik unsur kimia menunjukkan bahwa setidaknya ada tiga gas mulia lagi yang mungkin ada.