## Chemistry and Chemical Reactivity (9th Edition)

a) Image attached b) The most common oxidation state is +3. The Electron Configuration of Gd$^{3+}$ is [Xe]$4f^{7}$
a) Image attached b) The most common oxidation state is +3 because it corresponds to the loss of the two $6s$ and one $5d$ electrons. If we use noble gas notation we get the Electron Configuration of Gd$^{3+}$ to be [Xe]$4f^{7}$