Question

In which of the following crystal system 120° axial angle is present? [NCERT Pg. 10] (1) Orthorhombic (2) Tetragonal (3) Hexagonal (4) Cubic​

Answer 1

Answer:

n Bravais lattices with cubic systems, the following relationships can be observed. a = b = c . = = = 90 o. The 3 possible types of cubic cells have been illustrated below. These three possible cubic Bravais lattices are – Primitive (or Simple) Cubic Cell (P) Body-Centered Cubic Cell (I) Face-Centered Cubic Cell (F) Examples: Polonium has a simple cubic structure, iron has a body-centered cubic structure, and copper has a face also

Explanation:

Answer 2

Answer:

The axial angle of 120° is present in Hexagonal crystal system.

Therefore the option (3) is correct.

Explanation:

• The angle between any two adjacent faces of a crystal system is called interfacial angle. They are represented by α, β and γ.
• In Cubic system, the all interfacial angles are equal to 90°. Therefore, $\alpha = \beta = \gamma = 90^{o}$. It is most symmetric crystal system.
• In Tetragonal system, again all the interfacial angles are equal to 90° and , $\alpha = \beta = \gamma = 90^{o}$.
• In Hexagonal crystal system, the two angles are equal to 90° but the third axial angle is equal to 120°. Therefore, α = β =  90° and γ= 120°.
• In Orthorhombic crystal system, again all angles are equal to 90°.