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Most solid elements (metals and nonmetals) and compounds exist in crystal form. A crystalline solid is made up of atoms, molecules, or ions that are structured in a highly ordered microscopic structure that spans all directions. Examples include table salt (NaCl), sugar (sucrose), diamond, quartz, silver iodide, and other crystalline substances.
The structural constituents of a crystalline solid are arranged in a precise sequence. This recurring pattern may be found throughout the solid. Due to the constant occurrence of this precise pattern, a crystalline solid has a geometrical form that is characteristic to the substance’s nature. A particular pattern is repeated regularly in crystalline materials. This consistent pattern may be found throughout the crystal’s three-dimensional network.
Classification of Crystalline solids
A crystalline solid is one in which the component particles are organised in a regular pattern with long-range order. Distinct crystalline solids might have various structural units (atoms, molecules, or ions) and cohesive forces holding them together in the crystal. The composition of the component particles and the interaction forces existing between them can classify crystalline solids into distinct groups.
- Ionic solids
- Covalent solids
- Metallic solids
Ionic Bonds
Electrons leap orbits to link with the relevant supporting atom when ionic crystals form. Ions are stabilised by a mixture of negatively and positively charged electrostatic forces. These electrostatic forces, often known as Coulombic forces, were described as a law by scientist Charles Augustin de Coulomb. The attractive forces created between the atoms, according to Coulomb’s law, pull the atoms together, and this action is adversely duplicated due to the identical charges between the same ions. As a result, the atoms in the crystals form an extremely strong link. These crystals have high melting temperatures and stiff shapes due to these tremendous pressures.
Covalent Bonds
A covalent bond is a crystal structure where the electrons do not exit their orbits, as the name implies. Electrons, on the other hand, are shared by two atoms. Every two neighbouring atoms are connected by a common electron in this way. The bonded atoms share an additional electron with the atoms next to them, and so on. The creation of a geometrical crystal is the outcome of covalent bonding in between atoms of a material.
Metallic Bonds
All electrons from atomic orbits break loose from their trajectories during the creation of metallic crystals. These generate a cloud when they clump together. The positively charged cores of the atoms attract the entire cluster. The atoms are held together by this attraction. This sort of crystal may be found in all metals. The crystals created are very conductive because the electrons in the compound are free to move around.
Differences between ionic and covalent bonds
Ionic Bonds | Covalent Bonds |
Metal and nonmetal combine to generate this sort of relationship. Because the nonmetal pulls the electron, it’s as if the metal gives it one of its electrons. | This bond is generated when two nonmetals with identical electronegativities come together. In their outer orbitals, atoms share electrons. |
They do not possess any definite shape | They possess a definite shape |
They have high melting point | They have low melting point |
They have high boiling point | They have low boiling point |
They are solids at room temperature | They are either liquids or gas at room temperature |
Conclusion
Gases, liquids, and solids exist, with the arrangement of atoms becoming more organised as they proceed from gases to solids. In a pressure-temperature plot known as a phase diagram, the stable fields for the 3 states of a chemical element or compound are illustrated.
Crystal structure, colour, lustre, cleavage, density, and hardness are all physical qualities of minerals seen in hand specimens. Because minute levels of contaminants may change the colour of certain minerals, colour can be deceiving. The basic atomic structure influences density, and hardness.
Metallic bonding, in which a ‘sea’ of electrons holds the metal cations strongly together, resulting in dense, closely packed structures; ionic bonding, in which electrons are transferred between atoms, resulting in positive and negative ions that are strongly attracted to one another; and covalent bonding, in which electrons are shared, tends to result in open, low-density crystal structures that are strongly bonded. Ionic compounds make up around 90% of all minerals.
