Write out the ground-state electron configurations of (a) \(\mathrm{Ti}^{3+}\) (b) \(\mathrm{Ru}^{2+},(\mathrm{c}) \mathrm{Au}^{3+}\) (d) \(\mathrm{Mn}^{4+}\).

Refer to the periodic table and identify the atomic number (number of protons) of the neutral atoms. The atomic numbers of the elements in question are: (a) \(\mathrm{Ti} (Titanium) : 22\) (b) \(\mathrm{Ru} (Ruthenium) : 44\) (c) \(\mathrm{Au} (Gold) : 79\) (d) \(\mathrm{Mn} (Manganese) : 25\)

Using the periodic table and the aufbau principle, write the ground-state electron configuration of the neutral atom. (a) \(\mathrm{Ti} (Atomic\ number\ 22): [Ar] 4s^2 3d^2\) (b) \(\mathrm{Ru} (Atomic\ number\ 44): [Kr] 5s^2 4d^6\) (c) \(\mathrm{Au} (Atomic\ number\ 79): [Xe] 6s^2 4f^{14} 5d^{10}\) (d) \(\mathrm{Mn} (Atomic\ number\ 25): [Ar] 4s^2 3d^5\)

To write the electron configuration of the given ions, remove electrons according to the charge on the ion. Electrons are removed first from the outermost shell (highest principal quantum number, n) and then from the most energetic subshell (highest angular momentum quantum number, l). (a) \(\mathrm{Ti^{3+}}: [\, \, ]\) Remove 2 electrons from the 4s subshell and 1 electron from the 3d subshell: \([Ar]\, 3d^1\) (b) \(\mathrm{Ru^{2+}}: [\, \, ]\) Remove 2 electrons from the 5s subshell: \([Kr] \, 4d^6\) (c) \(\mathrm{Au^{3+}}: [\, \, ]\) Remove 2 electrons from the 6s subshell and 1 electron from the 5d subshell: \([Xe] \, 4f^{14}\, 5d^9\) (d) \(\mathrm{Mn^{4+}}: [\, \, ]\) Remove 2 electrons from the 4s subshell and 2 electrons from the 3d subshell: \([Ar]\, 3d^3\) The ground-state electron configurations of the given ions are: (a) \(\mathrm{Ti}^{3+}: [Ar]\, 3d^1\) (b) \(\mathrm{Ru}^{2+}: [Kr] \, 4d^6\) (c) \(\mathrm{Au}^{3+}: [Xe] \, 4f^{14}\, 5d^9\) (d) \(\mathrm{Mn}^{4+}: [Ar]\, 3d^3\)