Question

In the unit cell of galena, six square faces of equal size each form 90 degree angles with every adjacent face. What type of crystal system is this?
tetragonal
hexagonal
triclinic
cubic

Answer 1

Answer : The correct option is, Cubic.

Explanation :

As there are seven types of crystal systems which are cubic, tetragonal, orthorhombic, monoclinic, triclinic, rhombohedral and hexagonal.

A unit cell is characterized by the axial length (a, b and c) and axial angle $(\alpha ,\beta ,\gamma )$ parameters which decide the size and shape of the unit cell.

In tetragonal crystal system, $a=b\neq c$ and $\alpha=\beta=\gamma=90^o$

In hexagonal crystal system, $a=b\neq c$ and $\alpha=\beta=90^o,\gamma=120^o$

In triclinic crystal system, $a\neq b\neq c$ and $\alpha\neq \beta\neq \gamma=90^o$

In cubic crystal system, $a=b=c$ and $\alpha=\beta=\gamma=90^o$

Hence, the correct option is, Cubic.