There are seven crystal systems and six crystal families. They are :

1. Triclinic

2.Monoclinic

3.Orthorhombic

4.Rhombohedral

5.Tetragonal

6.Hexagonal

7.Cubic

Explanations given below –

**Triclinic crystal system **: In crystallography, the triclinic crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system In addition, none of the three vectors are orthogonal to another. The triclinic lattice is the least symmetric of the 14 three dimensional Bravais lattices. It has the minimum symmetry all lattices have: points of inversion at each lattice point and at 7 more points for each lattice point: at the midpoints of the edges and the faces, and at the center points. It is the only lattice type that itself has no mirror planes.

Example : K2Cr2O7 (Blue Vitriol)

2.**Monoclinic crystal system**: In crystallography, the monoclinic crystal system is one of the seven lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system They form a rectangular prism with a parallelogram as its base. Hence two pairs of vectors are perpendicular while the third pair makes an angle other than 90 degree.

Two monoclinic Bravais latices exist: the primitive monoclinic and the centered

monoclinic lattices(Base centered), with layers with a rectangular and rhombic lattice, respectively.

Example : Gypsum,Monoclinic sulphur

3.**Orthorhombic crystal system** : In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors,resulting in a rectangular prism with a rectangular base (a by b) and height (c), such

that a, b, and c are distinct. All three bases intersect at 90 degree angles. The three lattice vectors remain mutually orthogonal.

There are four orthorhombic Bravais lattices. simple onthorhombic, body-centered orthorhombic, base centered orthorhombic and face-centered orthorhombic

Example : BaSO4,KNO3,Rhombic sulphur

4. **Rhombohedral crystal system**: In crystallography, the rhombohedral crystal system is one of the seven crystal systems. Crystals in the rhombohedral lattice system are always in the trigonal crystal system. The rhombohedral crystal system consists of the rhombohedral lattice.

There are two descriptions of the rhombohedral

lattice system- Hexagonal axes and Rhombohedral axes.

Example : NaNO3,Ice

5. **Tetragonal crystal system**: In cystallography, the tetragonal crystal system is one of the 7 lattice point groups. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (a by a) and height (c, which is different from a).

There are two tetragonal crystal structure types. Bravais lattices: the simple tetragonal (from stretching the simple-cubic lattice) and the centered tetragonal (from stretching either the face centered or the body centered cubic lattice)

Example : Sn,SnCl2,SnO2

6.**Hexagonal crystal system**: In crystallography, the hexagonal lattice system is one of the 7 lattice systems, and the hexagonal crystal family is one of the 6 crystal families. The hexagonal lattice system consists of just one Bravais lattice type: the hexagonal one.

Example : Graphite,Quartz.

7.**Cubic crystal system**: In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main Bravais lattices, They are: Primitive cubic, Body-centered cubic and

Face-centered cubic

Example :NaCl,Ag,Diamond

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