Question

Assertion (A): Triclinic system is the most unsymmetrical system.

Reason (R): No axial angle is equal to ${90}^o$ in the triclinic system.

Choose the correct option.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is incorrect
• D. (A) is incorrect but (R) is correct
• E. Both (A) and (R) are incorrect

Answer 1

The correct option is B Both (A) and (R) are correct but (R) is not the correct explanation of (A)

The edges of the triclinic system are not equal as $a\ne b\ne c$. Hence, it is known as the most unsymmetrical system.

Name of System	Axes	Angles	Bravais Lattices
Cubic	$a=b=c$	$\alpha =\beta =\gamma ={90}^o$	Primitive, Face -centred, Body centred$=3$
Tetragonal	$a=b\ne c$	$\alpha =\beta =\gamma ={90}^o$	Primitive, Face -centred, Body centred$=2$
Rhombohombic or trigonal	$a=b=c$	$\alpha =\beta =\gamma \ne {90}^o$	Primitive$=1$
Orthorhombic or Rhombic	$a\ne b\ne c$	$\alpha =\beta =\gamma ={90}^o$	Primitive, Face -centred, Body centred End centred$=4$
Monoclinic	$a\ne b\ne c$	$\alpha =\gamma ={90}^o;\beta \ne {90}^o$	Primitive, End-centred$=2$
Triclinic	$a\ne b\ne c$	$\alpha \ne \beta \ne \gamma ={90}^o$	Primitive$=1$
Hexagonal	$a=b\ne c$	$\alpha =\beta ={90}^o\gamma ={90}^o$	Primitive $=1$ total $=14$