Free Crystal Lattice MCQs with Answers

1. The smallest repeating portion of a crystal lattice that shows the full symmetry of the crystal is called the

• A. unit cell
• B. crystal face
• C. lattice point
• D. domain

Explanation: Stacking the unit cell repeatedly in three dimensions generates the entire crystal, so knowing its dimensions and contents describes the whole structure. A lattice point is a single position within that cell rather than the repeating block itself. The seven crystal systems are classified by the shapes and angles the unit cell can take.

2. The number of crystal systems into which all crystals are classified is

• A. four
• B. seven
• C. fourteen
• D. twenty

Explanation: There are seven crystal systems, defined by the relative lengths of the unit cell axes and the angles between them, the cubic system being the most symmetrical. These give rise to fourteen Bravais lattices when the different centring arrangements are counted, which is why fourteen is offered as a distractor. Sodium chloride belongs to the cubic system.

3. In a unit cell of a crystal lattice the angle beta is between faces:

• A. a and b
• B. b and c
• C. c and a
• D. Not specified

Explanation: By convention the three interfacial angles of a unit cell are alpha between the b and c axes, beta between c and a, and gamma between a and b, each angle being named after the axis it does not lie against. Together with the three edge lengths, these six parameters define the cell completely. The Greek letter did not print cleanly in the original paper, appearing there as a stray character.