"Two, Ten, and Eighteen respectively. There's been controversy over the placement of hydrogen and helium on the periodic table, though. When the noble gases were discovered back around 1900, they were known as group 0, because the elements were believed to have no chemical reactivity. Unlike most of the other noble glasses, helium has only two electrons in its closed electron shell's outermost electron orbital. The rest of the noble gases have eight. Some assign helium directly above neon in group 18 instead."

Peter takes a breath, then looks back at Liz.