# Crystal Structure, Unit Cell, Crystal Systems, the Seven Crystal Systems (For CBSE, ICSE, IAS, NET, NRA 2022)

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## Crystal Structure

• A crystal structure is made of atoms. A crystal lattice is made of points. A crystal system is a set of axes. In other words, the structure is an ordered array of atoms, ions or molecules.
• Crystal Structure is obtained by attaching atoms, groups of atoms or molecules. This structure occurs from the intrinsic nature of the constituent particles to produce symmetric patterns. A small group of a repeating pattern of the atomic structure is known as the unit cell of the structure.
• A unit cell is the building block of the crystal structure and it also explains in detail the entire crystal structure and symmetry with the atom positions along with its principal axes. The length, edges of principal axes and the angle between the unit cells are called lattice constants or lattice parameters.

## Unit Cell

• Crystals use x-rays, which excite signals from the atom. The signals given by these atoms have different strengths and they usually depend upon the electron density distribution in closed shells. The signals released by the atoms varies. Lighter the atoms, weaker is their signals. The mutual arrangement of atoms is also known as crystal structures. Crystal structures are derived from the physical density and chemical formulas of solids.
• Unit cell can be defined as the smallest part of a component of the crystal. A group of atoms, ions or molecules, which are arranged together in a pure manner to build the crystal. The unit cells are structured in three-dimensional space, which describes the bulk arrangement of atoms of the crystal.

## Crystal Systems

• A Crystal System refers to one of the many classes of crystals, space groups, and lattices. In crystallography terms, lattice system and crystal, the system are associated with each other with a slight difference. Based on their point groups crystals and space groups are divided into seven crystal systems.
• The Seven Crystal Systems is an approach for classification depending upon their lattice and atomic structure. The atomic lattice is a series of atoms that are organized in a symmetrical pattern. With the help of the lattice, it is possible to determine the appearance and physical properties of the stone.
• It is possible to identify so as to which crystal system they belong to. In a Cubic System crystal are said to represent the element earth. They are Seven Crystal Systems and are stated below with illustrated examples.

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