Among \( \mathrm{Fe^{2+}} \), \( \mathrm{Fe^{3+}} \), \( \mathrm{Cr^{2+}} \) and \( \mathrm{Zn^{2+}} \), the ion that shows positive borax bead test and with highest ionization enthalpy is:
\( \mathrm{Fe^{2+}} \)
\( \mathrm{Zn^{2+}} \)
\( \mathrm{Cr^{2+}} \)
\( \mathrm{Fe^{3+}} \)