What Is the Difference Between Ionic and Covalent Bond with Examples
Bonding in covalent and ionic compounds is classified according to the character of electrons, which are delocalized. This classification is based on electronic effects, for which bonding is a result of interaction among electrons of different orbitals and hence is a chemical bonding. As a result of this interaction, electrons become shared by two or more nuclei, leading to a reduction in the electron energy and therefore stabilization of the compound. A compound whose nucleus accepts an electron is termed an electron acceptor and a nucleus that donates a single electron is an electron donor.
The delocalized electron is called the valence electron, which can be donated by a nucleus. Electrons in orbitals can be assigned energies concerning the nucleus of the atom. For example, an electron in the 1s orbital, which is localized around a nucleus, has high energy, and when the atom gains energy, the electron is donated to the nucleus to make the atom more stable. For an atom to be stable, it must gain the maximum amount of energy, and hence it is called a 'maximum donor'. Electrons with high energy are called 'high valence' or 'heavier' electrons.
The bond between atoms can be classified as either covalent or ionic following the number of electrons transferred. The number of transferred electrons to bond with a molecule to make it more stable is termed the valence. In a chemical bonding reaction, a bond with one electron transferred is termed a single bond, two electrons transferred is a double bond, three electrons transferred is a triple bond, and the maximum bond strength is denoted by a covalent bond. In general, the higher the valence of an atom, the stronger the bond between them is.
The chemical bonding of atoms can be classified as one of the following: ionic, covalent, metallic and van der Waals. Among these, ionic is a bond formed when two or more elements share electrons in their outer shells. However, all ionic bonds are not created equally. There are covalent, metallic and van der Waals bonds in ionic bonding.
Covalent Bonding
In a covalent bond, the nucleus of an atom accepts electrons of the other atom. The electron configuration is as follows:
There is one outer shell electron for both the donor and the acceptor atom.
One orbital is the highest in energy, which accounts for the greater bonding in covalent bonding.
The bond energy is the highest among all of the types of chemical bonding, owing to the greatest attractive force.
In a covalent bond, the bond energy is approximately 2-3 kcal mol−1 more than in an ionic bond. To illustrate the above-stated principle, in an electron exchange reaction in which one electron is transferred from donor atom A to the acceptor atom B, the nuclei of the atoms become ionic and the electron configuration of the atoms change from 2 _n_ − 2 to _n_ + 2. A covalent bond is considered when the electron configuration becomes 2 _n_ + 1 (in a diatomic molecule, the two atoms are of the same type).
Metallic Bonding
In a metallic bond, the electrons of the nucleus of both the atoms are shared between them, unlike the covalent and ionic bonds. The electrons form new chemical species which do not exist individually. The electrons cannot be assigned individually to the nucleus, and the two molecules share each electron in common.
Metallic bonds are extremely strong and they form through s-p mixing in d-orbitals.
In a metallic bond, the bond energy is lower than covalent bonding. However, owing to strong forces and a low percentage of electrons, the bond energy is weak and the bonds are easily broken.
Van der Waals Bonding
Van der Waals (vdW) bonding is similar to ionic bonding. One of the atoms in the molecule is ionic and the other is electrically neutral. In van der Waals bonding, the electrically neutral atom attracts the ionic atom. The interaction between the neutral atom and the ionic atom is of an opposite sign than that of the covalent bonds. This leads to attractive force and attraction between them. The strength of van der Waals bonding is not so strong.
Ionic Bonding
An ionic bond is very strong, owing to the presence of ions. The positive ions of one of the atoms are shared with the negative ions of the other atom. One of the atoms of the ionic compound has more electrons than the other. This one atom is positively charged. The electrically neutral atom has fewer electrons than the other atom. This atom is negatively charged. The charge on an atom increases or decreases if it loses or gains electrons, respectively.
Ionic bonding also involves an exchange interaction between the positive charge on one atom and the negative charge on the other atom. The covalent bonds of both atoms exist when the positive charge on one atom is neutralized by the negative charge on the other. Ionic bonding is different from ionic bonding in the following ways:
In an ionic bond, all the valence electrons are shared between two different atoms. In a covalent bond, only one valence electron of an atom remains.
In ionic bonding, the interaction between the positive charge on one atom and the negative charge on the other atom is not the same as the interaction between two like charges. In covalent bonding, both the interaction and force between two like charges are similar.
The charge separation of ions from an atom causes attraction. In covalent bonds, both the atom and the bonding electrons have the same charge.
Ions have higher mobility than non-polarized charges.
FAQs on Ionic and Covalent Bond Explained with Formation and Properties
1. What is the difference between ionic and covalent bond?
The main difference between an ionic bond and a covalent bond is that ionic bonds involve transfer of electrons, while covalent bonds involve sharing of electrons.
- Ionic bond: Formed when one atom transfers one or more electrons to another, creating oppositely charged ions (usually metal + non-metal).
- Covalent bond: Formed when two non-metal atoms share one or more pairs of electrons.
- Ionic compounds form crystal lattices (e.g., NaCl), while covalent compounds form molecules (e.g., H2O).
- Ionic bonds are typically stronger in solid state due to electrostatic attraction, while covalent bonds depend on shared electron pairs.
2. What is an ionic bond?
An ionic bond is a type of chemical bond formed by the complete transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.
- Usually occurs between a metal and a non-metal.
- Example: Sodium transfers one electron to chlorine to form Na+ and Cl-.
- The compound formed is NaCl, held together by electrostatic attraction.
- Ionic compounds typically have high melting points and conduct electricity when molten or dissolved in water.
3. What is a covalent bond?
A covalent bond is a chemical bond formed when two atoms share one or more pairs of electrons to achieve a stable electron configuration.
- Occurs mainly between non-metal atoms.
- Example: In H2, two hydrogen atoms share one pair of electrons.
- In water, H2O, oxygen shares electrons with two hydrogen atoms.
- Covalent bonds can be single, double, or triple depending on the number of shared electron pairs.
4. How is an ionic bond formed?
An ionic bond is formed when one atom loses electrons and another atom gains those electrons, creating oppositely charged ions that attract each other.
- Step 1: A metal atom loses electron(s) to form a positive ion (cation).
- Step 2: A non-metal atom gains electron(s) to form a negative ion (anion).
- Step 3: Electrostatic attraction between ions forms the ionic compound.
2Na(s) + Cl2(g) → 2NaCl(s)
Here, Na becomes Na+ and Cl becomes Cl-. This process is central to ionic bonding in chemistry.
5. How is a covalent bond formed?
A covalent bond is formed when two atoms share one or more pairs of valence electrons to complete their outer shells.
- Each atom contributes at least one electron to the shared pair.
- The shared electrons are attracted to the nuclei of both atoms.
- This sharing lowers the potential energy of the system.
H· + ·H → H–H (forming H2)
This sharing mechanism is key to understanding molecular bonding and Lewis structures.
6. What are the properties of ionic and covalent compounds?
Ionic and covalent compounds differ in melting point, conductivity, solubility, and physical state due to their bonding type.
- Ionic compounds:
- High melting and boiling points
- Conduct electricity when molten or in aqueous solution
- Usually soluble in water
- Form crystalline solids
- Covalent compounds:
- Lower melting and boiling points (except network solids)
- Poor electrical conductivity
- Often insoluble in water but soluble in organic solvents
- May exist as gases, liquids, or soft solids
7. What is a polar covalent bond?
A polar covalent bond is a covalent bond in which electrons are shared unequally due to a difference in electronegativity between atoms.
- Occurs when one atom attracts the shared electrons more strongly.
- Creates partial charges: δ+ and δ−.
- Example: In H2O, oxygen is more electronegative than hydrogen.
8. Can a bond be both ionic and covalent?
Most chemical bonds have both ionic and covalent character, but they are classified based on which character predominates.
- No bond is 100% ionic or 100% covalent.
- Greater electronegativity difference increases ionic character.
- Example: The bond in NaCl is mostly ionic but has slight covalent character.
9. Why do ionic compounds have high melting points?
Ionic compounds have high melting points because strong electrostatic forces of attraction exist between oppositely charged ions in the crystal lattice.
- These forces are called ionic bonds or electrostatic attractions.
- A large amount of energy is required to overcome lattice energy.
- Example: NaCl melts at about 801°C.
10. What are some examples of ionic and covalent bonds?
Common examples of ionic bonds include NaCl and MgO, while common examples of covalent bonds include H2O and CO2.
- Ionic bond example: Formation of magnesium oxide:
2Mg(s) + O2(g) → 2MgO(s) - Covalent bond example: Formation of carbon dioxide:
C(s) + O2(g) → CO2(g) - Ionic compounds involve metal + non-metal; covalent compounds involve non-metals only.
