Give the formulas for the ionic compounds made of the following ions:
sc3+ and br¯
k+ and o2¯
ca2+ and i¯
cr3+ and s2¯
rb+ and f¯
magnesium (mg) and oxygen (o) ions
potassium (k) and nitrogen (n) ions
strontium (sr) and fluorine (f) ions
aluminum (al) and sulfur (s) ions

ScBr3, K2O, CaI2, Cr2S3, RbF, MgO, K3N, SrF2, and Al2S3. The only thing you need to do is to ensure every ionic compound has a total valence of zero. Four the last four, you need to know usually valence of these ions.

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.