atom element atom in IUACP group An element classied in the IUACP group in the periodic table https://en.wikipedia.org/wiki/Periodic_table https://en.wikipedia.org/wiki/Group_(periodic_table) IUACP group element Oliver He, Kaiyong Liu International Union of Pure and Applied Chemistry (IUACP) Under an international naming convention, the groups are numbered numerically from 1 to 18 from the leftmost column (the alkali metals) to the rightmost column (the noble gases).