Two atoms form a covalent bond by sharing one or more electrons. The bond results from the electron-sharing interaction between the atoms, which holds the atoms together and gives them stability. Covalent bonds are strong and typically form between non-metal elements.
Covalent Bond Examples
These bonds are found in a wide range of substances, including gases, liquids, and solids. Some common examples of covalent bonds include:
Water (H2O): The bond between the hydrogen and oxygen atoms in water is a covalent bond. The hydrogen and oxygen atoms evenly share electrons, forming a nonpolar covalent bond.
Methane (CH4): The bond between the carbon and hydrogen atoms in methane is a covalent bond. The even sharing of electrons between the carbon and hydrogen atoms creates a nonpolar covalent bond.
Oxygen (O2): The bond between the oxygen atoms in oxygen is a covalent bond. The even sharing of electrons between the oxygen atoms results in a nonpolar covalent bond.
Carbon Dioxide (CO2): The bond between the carbon and oxygen atoms in carbon dioxide is a covalent bond. The uneven sharing of electrons between the carbon and oxygen atoms forms a polar covalent bond.
Covalent Bonds Formation
A covalent bond is formed when two or more atoms share electrons. This bond results in a stable, symmetrical arrangement of the electrons and atoms in a molecule. The sharing of electrons allows the atoms to fill their outer electron shells and become more stable, which is known as the octet rule. This rule states that atoms tend to form bonds in order to attain a full outer electron shell of eight electrons, as is the case in noble gases.
The formation of covalent bonds can be illustrated through the sharing of electrons between two hydrogen atoms. Each hydrogen atom has one electron in its outer electron shell, but it would like to have two electrons in its outer electron shell for stability. When two hydrogen atoms come together, they share their electrons, resulting in a covalent bond. This bond results in a molecule of hydrogen gas (H2), which is much more stable than the individual hydrogen atoms.
Types of Covalent Bonds
Based on single bonds, double bonds, and triple bonds.
Single Bonds: A single bond is formed when two atoms share one pair of electrons. This bond is represented by a single line between the atoms in a molecule. Single bonds are the most common type of covalent bond, and they are typically strong and stable.
Double Bonds: A double bond is formed when two atoms share two pairs of electrons. This bond is represented by two lines between the atoms in a molecule. Double bonds are typically stronger and less flexible than single bonds, and they result in a more rigid structure for the molecule.
Triple Bonds: Atoms form a triple bond when they share three pairs of electrons. This bond is represented by three lines between the atoms in a molecule, symbolizing its strength as the strongest type of covalent bond. Molecules such as nitrogen (N2) and acetylene (C2H2) frequently exhibit this strong bond, making it an important aspect of chemical bonding. The sharing of three pairs of electrons results in a stable bond that holds the molecule together.
Based on Polarity, Covalent Bonds can be:
Nonpolar Covalent Bonds: Nonpolar covalent bonds occur when two atoms have the same electronegativity and therefore share electrons equally. The resulting bond is nonpolar, meaning that there are equal amounts of electrons on each atom and there is no net positive or negative charge. Examples of these bonds include the bond between hydrogen and hydrogen (H2), and the bond between carbon and hydrogen (CH4).
Polar Covalent Bonds: Polar covalent bonds occur when two atoms have different electronegativities and therefore share electrons unevenly. The resulting bond is polar, meaning that the electrons are more attracted to one atom than the other, resulting in a net positive or negative charge. Examples of these bonds include the bond between oxygen and hydrogen (H2O), and the bond between nitrogen and hydrogen (NH3).
Coordinate Covalent Bond: One atom forms a coordinate covalent bond by providing both electrons to the bond. This type of bond is also known as a dative bond or a coordinate bond. In a coordinate covalent bond, only one atom acts as the electron donor, while the other atom acts as the electron acceptor. This type of bond is common in complexes and coordination compounds, and it is essential for many biological processes, such as enzymes and metabolic pathways.
Properties and Characteristics of Covalent Bond
Covalent bonds have several important properties and characteristics that affect the structure, properties, and behavior of substances.
Electronegativity: Electronegativity is the ability of an atom to attract electrons towards itself. In covalent bonds, the electronegativity difference between the atoms determines the type of bond that will form. If the electronegativity difference is small, a single bond will form. If the electronegativity difference is larger, a double or triple bond may form.
Polarity: Covalent bonds can be polar or nonpolar. In a nonpolar covalent bond, the atoms share electrons equally without any difference in electronegativity. In a polar covalent bond, the difference in electronegativity between the atoms leads to an uneven sharing of electrons.
Bond Length: The bond length is the distance between the nuclei of the two atoms in a covalent bond. The bond length is affected by the size of the atoms, the number of bonds between the atoms, and the type of bond. In general, double bonds have a shorter bond length than single bonds, and triple bonds have a shorter bond length than double bonds.
Bond Energy: Bond energy is the amount of energy required to break a bond. Covalent bonds have relatively high bond energy compared to ionic bonds, making them strong and difficult to break. The bond energy of these bonds depends on the type of bond and the atoms involved in the bond.
Reactivity: The reactivity of covalent bonds depends on the stability of the bond. Single bonds are typically more reactive than double or triple bonds because they are less stable and have a higher bond energy.
List of Covalent Compounds
| Single Bond | Double Bond | Triple Bond |
| Methane (CH4) | Ethene (C2H4) | Acetylene (C2H2) |
| Ethane (C2H6) | Acetylene (C2H2) | Ethyne (C2H2) |
| Propane (C3H8) | Carbon monoxide (CO) | Nitrogen gas (N2) |
| Ammonia (NH3) | Ethyne (C2H2) | Diazomethane (CH2N2) |
| Water (H2O) | Formaldehyde (CH2O) | Cyanogen (CN2) |
| Hydrogen sulfide (H2S) | Oxirane (C2H4O) | Cyanoacetylene (HC3N) |
| Carbon dioxide (CO2) | Nitrous oxide (N2O) | Ethyne oxide (C2H2O) |
| Nitrogen gas (N2) | Ozon (O3) | Acrolein (CH2=CHCHO) |
| Oxygen gas (O2) | Propene (C3H6) | Isocyanic acid (HNCO) |
| Dichloromethane (CH2Cl2) | Butadiene (C4H6) | Cyanogen chloride (CNCl) |