Perovskite, a mineral containing calcium, oxygen and titanium crystallises in the given cubic unit cell,  the oxidation number of titanium in this mineral is?

Calcium appears at the eight corners.

Hence, number of calcium atom = $\frac{8}{8}=1$

Oxygen appears on six faces and two faces share one oxygen atom.

Hence, number of oxygen atom $\frac{6}{2}=3$

Titanium appears at the centre hence, number of titanium atom = 1

Thus, perovskite has formula CaTiO₃

if oxidation number of Ti = x

Then$$\begin{gathered} \underset{\downarrow }{\mathrm{Ca}} \underset{\downarrow }{\mathrm{Ti} } \underset{\downarrow }{{\mathrm{O}}_3} \\ 2 + \mathrm{x} - 6 = 0 \\ \therefore \mathrm{x} = 4 \end{gathered}$$

Thus, oxidation number of Ti = +4