What is Ionic Bond?
Ions are formed when an atom or molecule has a net charge. They can have a net negative charge or a positive charge. Oppositely charged species attract each other. Ionic bond is formed due to electrostatic attraction between oppositely charged ions.
When a highly electronegative element comes close to another electropositive element, it plucks an electron from the electropositive element and the complete transfer of electron from one element to another forms the ions. They combine due to electrostatic attraction to form the ionic bond. Ionic bond is also known as electrovalent bond.
Ionic Bond Properties
1) Ionic compounds are usually solid. The ionic bonds hold the atoms strongly due to electrostatic attraction. The ionic compounds have high lattice energy, making them stable solids at room temperature.
2) Ionic compounds are soluble in polar solvents like water but are insoluble in non-polar solvent like benzene. The ionic compounds can break up due to ionic dipole interaction, where the polar solvent molecules can solvate the individual charge. The energy of dissolution compensates for the energy of the ionic bond.
3) The ionic compounds form a strong lattice due to strong electrostatic force operating over longer distances. Higher energy is required to disrupt their physical structure and as a result, ionic compounds usually have a very high melting point and boiling point.
4) The electrostatic attraction of the ionic bonds helps them in organising crystal structures. Crystal structures are arrangements of ions in repetitive units extended in three dimensions. This makes ionic solids highly dense.
5) Ionic crystals are however quite brittle. Applying pressure from outside, such as hammering, pushes the atoms too close to each which results in strong repulsive force. This increases their brittleness.
6) Ionic forces are non-directional, i.e, the electrostatic forces act in all directions equally. Ionic compounds do not have any isomers because the compounds are non-directional as well. The crystal lattice which is the unit arrangement of ions repeats in all directions equally and hence appears the same from all dimensions.
7) Solid ionic compounds cannot conduct electricity, however, in molten state, they can conduct electricity owing to the dissociation of charges.
How are Ionic Bonds Formed?
Ionic compounds are mostly formed by the combination of metals and non-metals. Metals are highly electropositive in nature and nonmetals are electronegative; the transfer of electrons is complete between metals and non-metals, as a result they form a strong ionic bond.
Let’s take for example NaCl, the electronic configuration of sodium 1s2 2s2 2p6 3s1 indicates a single electron in the outermost shell, and chlorine 1s2 2s2 2p6 3s2 3p5 has one electron short of completing its octet. Sodium completely transfers its valence of electron to chlorine
Na → Na+ + e-
Cl + e- → Cl-
This satisfies the octet of sodium and chlorine, and both form an ionic bond. The resulting compound is sodium chloride (NaCl), known as rock salt.
Factors Affecting Ionic Bond
The nature of the elements involved in the bonding affects the ionic bonds; some of the factors affecting the ionic bonds are listed below:
Ionisation Energy: Metals with low ionisation energy can easily lose electrons and can form ionic bonds very easily. Alkali metals and alkaline earth metals are the most electropositive elements, as we go down the group, the atomic size increases and ionisation energy decreases; as a result, these metals can readily lose an electron and participate in ionic bonding.
Electron Affinity: Atoms which can readily accept electrons and become negatively charged have high electron affinity. Atoms with high electron affinity will be able to form stable anions. Elements of group 6 and 7 have high electron affinity and can form ionic bonds easily. As the atomic size increases down the group, electron affinity decreases.
Lattice Energy: Lattice energy is the energy released when one mole of ionic compounds is formed by the combinations of anions and cations. The energy released following the ionic bond formation is the lattice energy and the higher the energy released the more stable is the compound.
Lattice energy depends on: the size of the ions and the charge on the ions.
Small ions have high charge to size ratio and have stronger force of attraction resulting in stronger ionic bond.
Higher charge also causes strong attraction between the ions resulting in stronger ionic bonds.
Key Features
Ionic bonds are formed between two elements with considerable differences in electronegativity.
A highly electronegative element and an electropositive element come together to form ionic bond.
Ionic bonds are formed as a result of electrostatic attraction between the two elements. It involves complete transference of electrons from one element to the other.
Interesting Facts
Humans have been using common salt which is NaCl for 8000 years. Now NaCl is one of the most basic and common of the ionic compounds that still finds its daily use.
Metals are found as ionic compounds in their ores.
FAQs on Ionic Bond
1. Why does the sugar solution not conduct electricity?
The sugar solution is a covalent compound but not an ionic compound and hence it has only molecules in it but not the ions. So the sugar solution cannot conduct electricity.
2. Why do Ionic compounds have high melting and boiling points?
The constituents of ionic compounds i.e. oppositely charged particles are held together by strong electrostatic forces of attraction. Therefore, a large amount of heat is supplied to separate the constituents from their lattice. So to melt or boil ionic compounds a large amount of lattice energy is needed. Hence, electrovalent or ionic compounds have high melting and boiling points.
3. Why molten Sodium Chloride conducts electricity?
Molten Sodium Chloride conducts electricity because the electrostatic forces of attraction are overcome by heat energy. Therefore, the ions become free to carry electric current.
4. What is a co-ordinate bond?
Co-ordinate bond is defined as that bond in which the sharing of electrons takes place on the part of entirely one atom. For Example- Formation of ammonium ion is due to co-ordinate bond.
5. What are reducing agents?
Reducing agents are those metals which donate electrons to reach stable electronic configuration. Hence metals are called electron donors.
6. What are the oxidizing agents?
Oxidizing agents are those non-metals which accept electrons to reach stable electronic configuration. Hence non-metals are called electron acceptors.
7. Why does solid sodium Chloride does not conduct electricity?
Sodium Chloride does not conduct electricity because the oppositely charged ions in Sodium Chloride are held by a strong electrostatic force of attraction and hence the free ions are absent to carry electric current.
8. What is a covalent bond?
A covalent bond is defined as that bond which is formed by mutual sharing of electrons. For Example- formation of Chlorine molecule is due to covalent bonding.
9. State two properties of covalent compounds?
Covalent Compounds have low melting and boiling point
Covalent compound is soluble in organic solvents like Benzene and Phenol
10. State three factors that an atom should have for participating in covalent bonding.
1. High Electro-negativity
2. High Ionization Energy
3. High Electron affinity.
11. Name the followings:
The type of bonding present in metallic chlorides- Ionic Bond
The electrons present in the outermost shell of an atom- Valence electrons
Outermost shell of an atom- Valence shell
12. What is electronegativity and electropositivity?
Electronegativity is the property of an atom, whereby the atoms exhibit a tendency to attract the electron density while forming a bond. Electropositivity is the opposite of electronegativity, it is the tendency of an atom to donate its valence electrons.
13. What is a chemical bond?
Chemical bond is the attraction between two atoms. Two atoms come close to an appropriate distance to fulfil their octet, the bond energy is the energy released upon octet satisfaction and results in the formation of bond.
14. What are some non-ionic compounds that form crystals?
Crystals are solid compounds which have highly ordered structures, with the atoms or molecules arranged in specific patterns. Some nonionic compounds found in crystals are sugar, diamond, graphite etc.
