Crystal Structure of NaCl

 Introduction: Crystal Structure of NaCl

We know that atoms are very small particles that make all the matter. Atom is the basic unit and in turn, it is composed of three major particles called electrons, protons, and neutrons. The protons and neutrons combinedly are at the Centre of the atom and are called the nucleus, whereas the electrons revolve around the nucleus. 

Each element is made of atoms. The group of atoms together is called the compound. The compounds are the combination of one element or more than one element. The strength of the compound depends on the structure of the atoms in the compounds and the charged particles in the compound. The unstable elements combine with other elements to form a compound. The bonding of those elements can be of two types and they are: Ionic bond and Covalent bond. 

Bond:  

We already know that in an atom the electrons move around the nucleus. Nucleus contains protons that are positively charged particles, and the electrons are the negatively charged particles. The attractive force between the electrons and the protons in an element depends on the structure and the number of electrons and protons. Based on it, some elements are unstable as the nucleus cannot hold the electrons around them. They try to move to the other element forming a compound. This is called Bonding. These bonds are chemical bonds. 

Ionic bonding:  

The bonding of elements if done by one element giving away its electron to gain the stability to the other element is called the ionic bond. The compound formed through the giving away of the electron is called an ionic compound. The ionic bond occurs between the elements that are short of an electron for stability and another element that is excess of electron. 

Properties of Ionic compounds:  

These compounds are usually solid at room temperature. They can easily break apart. They have high melting and boiling points. The ionic compounds that dissolve in water are good conductors of electricity. The charges of the ions and the forces that hold them together in the compound are responsible for these properties of ionic compounds. 

Covalent bonding:  

The bonding of elements is done by sharing an electron. One element shares one of the electrons with another element. The shared electron travels in both the elements and makes the compound stable. The compounds formed through this manner are called covalent compounds. In a covalent bond the electron is shared between the two elements. The covalent bond is of different types. They are single covalent bond, double covalent bond and triple covalent bond. If we see two covalent bonds in a single compound, then we say that the compound is of double covalent bond. 

Properties of Covalent compounds: 

These compounds can be either solid, or liquid, or gas at room temperature. Usually, covalent compounds have the least boiling and melting points compared to the ionic compounds. The atoms in covalent compounds dissolve in the water as the ionic compounds do. The solution of the covalent compounds does not conduct the electricity and act as insulators.  

Crystals: 

The particles of different substances arrange themselves into different patterns when they solidify into crystals. A crystal is a regular, repeating arrangement of atoms, ions, or molecules.  

The best example of the crystal is a snowflake. In snowflakes, the water molecule freezes to form a six-sided pattern. A snowflake is an example of a molecular crystal. 

In some types of crystals, the solid is held by ionic bonds. The best of such a crystal with ionic bond is the sodium chloride or the common salt or table salt. They are called ionic crystals.  

The third type of crystals are covalent crystals. These types of crystals are bound together by covalent bonds. The examples of the covalent crystals are diamond and quartz.  

The structure of the crystal is important because it helps in understanding the crystal’s physical properties.  

Crystal patterns: 

Crystals are formed from the repeating patterns of the smaller parts. These smaller parts that are repeating are unit cells. A unit cell is the smallest repeating pattern in the crystal that shows how the atoms, ions, and molecules are arranged. 

Many solids exist as crystals. Whether a small tiny grain of table salt or a big block of quartz, a crystal’s shape often is a reflection of the arrangement of its particles.  

Hexagonal:  

Quartz crystals are six-sided just as a snowflake is. This is because the molecules that make up both quartz and snowflakes arrange themselves into hexagonal patterns. 

Cubic: 

Fluorite and sodium chloride form cube-shaped crystals. This shape is a reflection of the cube-shaped arrangement of the ions in the crystal.  

Sodium Chloride (NaCl): 

Sodium chloride, NaCl, is an ionic crystal. Every tiny grain of sodium chloride contains billions of sodium ions and chloride ions. Crystals of sodium chloride have a regular, cubic structure. The pattern in the sodium chloride is simple. Sodium ions alternate with chloride ions in a three- dimensional pattern. Ionic bonds hold the ions tightly. 

Characteristics of ionic and covalent bond: