Question:

Number of atoms in the unit cell of $Na ( BCC$ type crystal) and Mg (FCC type crystal) are respectively :

Updated On: Aug 15, 2022
  • 4,4
  • 4,2
  • 2,4
  • 1,1
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The Correct Option is C

Solution and Explanation

Na unit cell (body centred cubic) 8 corner atoms $\times \frac{1}{8}=1$ 1 atom placed inside the unit cell $=1$ Total atoms $=2$ Mg unit cell (Face centred cubic) 8 corner atoms $\times \frac{1}{8}=1$ 6 face atoms $\times \frac{1}{2}=3$ Total atoms $=4$
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Concepts Used:

Solid State

Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions. 

Solid State

Types of Solids:

Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;

  • Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
  • Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.