# Rank the elements in each of the following sets in order of decreasing First Ionization Energy IE$_1$: Sb, Te, Sn

$\begin{array}{1 1} Te > Sb > Sn \\ Te > Sn > Sb \\Sb > Sn > Te \\ Sn > Sb > Te \end{array}$

Answer: Te > Sb > Sn
IE decreases as you proceed down in a group; IE increases as you go across a period.
These are all in Period 5, IE increases across a period.