What is the ground state electron configuration of an atom of chromium, Cr (Z = 24)?

A. [Ar]3d⁶

B. [Ar]4s²3d⁴

C. [Ar]4s¹3d⁵

D. [Ar]4s²4p⁴

Which representation would be correct for a species, Z, which has 31 protons, 40 neutrons and 28 electrons?

A. ${}_{31}^{71}{\mathrm{Z}}^{3+}$

B. ${}_{31}^{71}{\mathrm{Z}}^{3-}$

C. ${}_{40}^{71}{\mathrm{Z}}^{3+}$

D.  ${}_{28}^{71}{\mathrm{Z}}^{3+}$

Which species has two more neutrons than electrons?

${}_3{}^{6}L{i}^{+}$             ${}_4{}^{9}B{e}^{2+}$             ${}_{11}{}^{23}N{a}^{+}$             ${}_{20}{}^{42}C{a}^{2+}$

A.  ${}_3{}^{6}L{i}^{+}$

B.  ${}_4{}^{9}B{e}^{2+}$

C.  ${}_{11}{}^{23}N{a}^{+}$

D.  ${}_{20}{}^{42}C{a}^{2+}$

Which is correct for ${}_{16}^{34}{\text{S}}^{2-}$?