Question

The most unsymmetrical crystal system is:
A.) cubic
B.) hexagonal
C.) triclinic
D.) orthorhombic

Answer 1

The most unsymmetrical crystal system is that in which the edges as well as the bond angles have least symmetry. In the triclinic crystal system, all the edge lengths and also all the bond angles are different from each other.

Complete step by step answer:
In this question, the crystal system refers to the seven crystal structures which are classified according to the symmetry of the unit cells. These seven structures are collectively known as crystal systems. These crystal systems are: Cubic, Hexagonal, Trigonal, Tetragonal, Orthorhombic Monoclinic, Triclinic. These crystal structures differ from each other on the basis of their symmetry that is their edge lengths and bond angles. The edge lengths or lattice sites are represented as $a,b{\text{ and c}}$ and bond angles are represented as $\alpha ,\beta {\text{ and }}\gamma$.
Now, we will discuss the lattice sites and bond angles of given options to find out the most unsymmetrical system.
In option A.), the cubic crystal system has all the edge lengths or bond sites equal as well as all the bond angles equal to each other. That is in the cubic crystal system we have $a = b = c$ and also $\alpha = \beta = \gamma$. It is the most symmetrical crystal system.
In option B.), the hexagonal crystal system two lattice sites are equal but not the third and two angles are of $90^\circ$ and the third angle is of $120^\circ$. In the hexagonal crystal system we have $a = b \ne c$ and $\alpha = \beta = 90^\circ ,\gamma = 120^\circ$.
In option C.), the triclinic crystal system all the lattice sites and all the bond angles are unequal. That is in the triclinic crystal system we have $a \ne b \ne c$ and $\alpha \ne \beta \ne \gamma \ne 90^\circ$. It is the most unsymmetrical crystal system.
In option D.) In an orthorhombic crystal system we have $a \ne b \ne c$ and $\alpha = \beta = \gamma = 90^\circ$.

Hence, option C.) is the correct answer.

Note:
Always remember that the cubic crystal system is the most symmetrical crystal system this is because in the cubic crystal system all the edge angles and also all the edge lengths are equal while the triclinic is most unsymmetrical.