## Chemistry: The Molecular Science (5th Edition)

$Rb+ \gt Ca 2+ \gt Mg 2+ \gt Be 2+$
We see that these ions all have the electron configuration of a noble gas. After seeing this, we must realize that the size of an atom increases as you move down the periodic table. We use this information to order the elements as follows: $Rb+ \gt Ca 2+ \gt Mg 2+ \gt Be 2+$