Name the Lanthanoid elements in the correct order and give their chemical symbols and electronic structures.

Work out the number of unpaired electrons in the ground state of the following ions:

${\mathrm{La}}^{3+}, {\mathrm{Ce}}^{4+}, {\mathrm{Lu}}^{3+}, {\mathrm{Yb}}^{2+}, {\mathrm{Gd}}^{3+}, {\mathrm{Eu}}^{2+}, {\mathrm{Tb}}^{4+}.$