Advice 1: How to determine the type of crystal lattice

A crystal is a body whose particles (atoms, ions, molecules) are not in chaotic, but in a very specific order. This procedure is repeated periodically, as if forming an imaginary "grid". It is considered that there are four types of crystal lattices: metallic, ionic, atomic and molecular. And how can you determine what type of crystal lattice has a particular substance?
How to determine the type of crystal lattice
As you can easily guess from the name, the metal lattice type found in metals. These substances are characterized by generally high melting point, metallic luster, hardness, are good conductors of electric current. Remember that the nodes in lattices of this type are either neutral atoms or positive ions. In between nodes the electron migration which provides a high conductivity similar substances.
Ionic crystal lattice type. Keep in mind that it is inherent in the oxides and salts. Typical example – all known crystals of table salt, sodium chloride. The nodes of such gratings alternately alternating positively and negatively charged ions. Such substances are generally refractory, with low volatility. As you can guess, they have an ionic type of chemical bonding.
The atomic type of the crystal lattice inherent in simple substances, non – metals, which under normal conditions represent a rigid body. For example, sulphur, phosphorus, carbon. The nodes of these lattices are neutral atoms, connected to each other via a covalent chemical bond. Such substances characteristic of refractoriness, insolubility in water. Some (for example, carbon in form of diamond) – extremely high hardness.
Finally, the last type of lattice - molecular. It is found in substances under normal conditions are in liquid or gaseous form. As, again, you can easily understand from the name, the nodes of these lattices, molecules. They can be as non-polar species (from simple gases such as Cl2, O2) and polar species (the most famous example – water H2O). Substances with this type of lattice does not conduct electricity, volatile, have low melting temperatures.
Thus, to confidently determine what type of crystal lattice has a particular substance, you ought to find out to what class of substances it is and what physico-chemical properties of has.

Advice 2 : What types of crystal lattices

In crystals of chemical particles (molecules, atoms or ions) arranged in a specific order, in certain conditions they form symmetrical polyhedrons. There are four types of crystal lattices — ion, nuclear, molecular, and metallic.
What types of crystal lattices


The crystalline state is characterized by the presence of long-range order in the arrangement of the particles and also by the symmetry of the crystal lattice. Solid crystals are three-dimensional structures that have the same element structure is repeated in all directions.

The correct form of the crystals is due to their internal structure. If they replace the molecules, atoms and ions points instead of the centers of gravity of these particles will be a three-dimensional regular distribution of the crystalline lattice. Duplicate the elements of its structure are called elementary cells, and points — nodes of the crystal lattice. There are several types of crystals, depending on the particles that constitute them, and the nature of the chemical bond between them.

Ionic crystal lattice

Ionic crystals form anions and cations, between which there is the ionic bond. The crystals are salts and hydroxides of most metals. Each cation r anion is attracted to and repelled by other cations, so ionic crystal it is impossible to distinguish single molecules. The crystal can be considered as one huge molecule, and its size is not limited, it is able to attach the new ions.

Atomic crystal lattice

In atomic crystals, the individual atoms United by covalent bonds. Like ionic crystals, they can also be regarded as a huge molecule. While atomic crystals are very hard and durable, do not conduct electricity and heat. They are practically insoluble, they tend to have low reactivity. Substances with a crystalline atomic lattices are melted at very high temperatures.

Molecular crystals

Molecular crystal lattice formed from molecules whose atoms are combined by covalent bonds. Because of this, between molecules are weak molecular forces. Such crystals have low hardness, low melting temperature and high fluidity. Substances that they form, and their melts and solutions do not conduct electric current.

Metal crystal lattice

In the crystal lattices of metals the atoms are arranged with maximum density, and their relationships are delocalized, they are distributed throughout the crystal. Such crystals are opaque, metallic luster different, easy to deform, with good conduct electricity and heat.

This classification describes only the limiting cases, most of the crystals of inorganic substances belong to the intermediate types — molecular covalent, covalent-ionic, etc. as example, a crystal of graphite, within each layer covalent he-metal and between layers — molecular.
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