Rank the following elements according to their ionization energy:
tin
krypton
antimony
arsenic

Order of increasing Ionization Energy is  Kr>As>Sb >Sn.

Explanation:

In the periodic table, the ionization energy increases when we move across the period also decreases when we move down the group. Tin (Sn) is in the carbon group, Arsenic and antimony is present in nitrogen group(Sb,As), and Krypton is present in Helium group(Kr). As we know, Helium or zero group elements have maximum ionization energy, since it has fulfilled orbitals, So Kr has the maximum ionization energy, where as As and Sb is present in lower periods than that of Krypton and then comes tin.So ionization energy is in the increasing order of  Kr>As>Sb >Sn.Hence the order follows as,Kryton>Arsenic>Antimony>Tin

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.