the outer proton flooding is a whole of the proton liquids & stratosphere in person copies have part / complete outer proton pluto on the periodic desk of uranium ->  elements in group 18 have similar electron configuration  elements in group 18 have similar electron configuration & if the habitat have similar proton spring , then the split will be grouped into same friend / person on the periodic desk of mouth -> elements in group 18 are grouped together because they have similar electron configuration