Grade 7
  1. Introduction to Chemistry  1.1. What is Chemistry?  1.2. Importance of chemistry in daily life  1.3. Branches of chemistry  1.4. Scientific Method in Chemistry  1.5. Laboratory Safety Rules and Precautions  1.6. Common Laboratory Equipment and Their Uses  1.7. Units of measurement in chemistry
  2. Matter and its properties  2.1. Definition of Matter  2.2. Classification of matter  2.3. Properties of matter  2.3.1. Physical properties  2.3.2. Chemical properties  2.4. States of matter  2.4.1. Solid state  2.4.2. Fluid state  2.4.3. Gaseous state  2.4.4. Plasma and Bose–Einstein condensates  2.5. Changes in the states of matter  2.5.1. Melting and freezing  2.5.2. Evaporation and Condensation  2.5.3. Sublimation and deposition  2.6. Density and its applications  2.7. Diffusion and its importance
  3. Elements, Compounds, and Mixtures  3.1. Definition of the element  3.2. Classification of elements  3.3. Metals, Nonmetals and Metalloids  3.4. Noble gases and their properties  3.5. Introduction to the Periodic Table  3.6. Definition of Compound  3.7. Properties of Compounds  3.8. Introduction to Chemical Formulas  3.9. Definition of Mixture  3.10. Types of mixtures  3.10.1. Homogeneous mixture  3.10.2. Heterogeneous mixtures  3.11. Difference Between Compounds and Mixtures  3.12. Solutions, Colloids and Suspensions
  4. Separation of mixtures  4.1. Need for separation of mixtures  4.2. Separation methods  4.2.1. Filtration  4.2.2. Sedimentation and decantation  4.2.3. Evaporation  4.2.4. Crystallization  4.2.5. Distillation  4.2.6. Chromatography  4.2.7. Magnetic Separation  4.2.8. Centrifugation
  5. Atomic Structure  5.1. Introduction to Atoms  5.2. Structure of the atom  5.2.1. Nucleus and electron cloud  5.3. Subatomic particles  5.3.1. Proton  5.3.2. Neutron  5.3.3. Electrons  5.4. Atomic number and mass number  5.5. Isotopes and their uses  5.6. Ions and ion formation
  6. Periodic table  6.1. Introduction to the Periodic Table  6.2. Groups and periods  6.3. Trends in the Periodic Table  6.3.1. Atomic Size  6.3.2. Metallic and non-metallic character  6.3.3. Electronegativity  6.3.4. Reactivity of the elements  6.4. Alkali metals and their properties
  7. Chemical bond  7.1. Why do atoms form bonds?  7.2. Types of chemical bonds  7.2.1. Ionic bond  7.2.2. Covalent bond  7.2.3. Metal Bond  7.3. Properties of Ionic and Covalent Compounds  7.4. Intermolecular forces
  8. Chemical reactions  8.1. Introduction to Chemical Reactions  8.2. Signs of a chemical reaction  8.3. Types of Chemical Reactions  8.3.1. Combination Reactions  8.3.2. Decomposition reactions  8.3.3. Displacement reactions  8.3.4. Double displacement reactions  8.3.5. Combustion reactions  8.4. Law of conservation of mass  8.5. Balancing simple chemical equations
  9. Acids, Bases and Salts  9.1. Definition of Acid and Base  9.2. Properties of Acids  9.3. Properties of bases  9.4. pH Scale and Indicators  9.5. Neutralization reactions  9.6. Common Acids and Bases in Everyday Life  9.7. Preparation and use of salts  9.8. Strong and weak acids and bases
  10. Solutions and Solubility  10.1. Definition of Solution  10.2. Components of the solution  10.2.1. Solvent  10.2.2. solute  10.3. Factors Affecting Solubility  10.4. Concentration of solutions  10.5. Saturated and unsaturated solutions  10.6. Colloids and suspensions  10.7. Solubility curve and its interpretation
  11. Air and atmosphere  11.1. Composition of air  11.2. Properties of gases in the air  11.3. Importance of Oxygen and Carbon Dioxide  11.4. Air pollution and its effects  11.5. Greenhouse effect and global warming  11.6. Ways to reduce air pollution  11.7. Ozone layer and its importance
  12. Water and its importance  12.1. Properties of Water  12.2. Water as the universal solvent  12.3. Importance of water for life  12.4. Water pollution and its effects  12.5. Water Purification  12.5.1. Filtration  12.5.2. boil  12.5.3. Chlorination in water purification  12.5.4. reverse osmosis  12.6. Hard and soft water  12.7. Water cycle and its importance
  13. Fuel and energy  13.1. Types of fuel  13.1.1. Fossil fuels  13.1.2. Renewable energy sources  13.2. Combustion and energy release  13.3. Global warming and its effects  13.4. Alternative sources of energy  13.5. Ways to conserve energy
  14. Metals and Nonmetals  14.1. Physical and chemical properties of metals  14.2. Physical and Chemical Properties of Non-Metals  14.3. Difference Between Metals and Nonmetals  14.4. Uses of metals and nonmetals  14.5. Corrosion of metals and its prevention  14.6. Alloys and their importance
  15. Plastics and polymers  15.1. Natural and synthetic polymers  15.2. Properties of plastics  15.3. Biodegradable and Non-Biodegradable Plastics  15.4. Environmental impact of plastic  15.5. Recycling and waste management in plastics and polymers  15.6. Daily Uses of Polymers
  16. Introduction to Organic Chemistry  16.1. Basic definitions of organic chemistry  16.2. Carbon Compounds in Daily Life  16.3. Hydrocarbons  16.4. Simple functional groups (alcohols and carboxylic acids)  16.5. Importance of organic compounds in industry

Grade 7 → Chemical bond → Types of chemical bonds ↓


Covalent bond


Chemical bonding is about atoms joining together to form molecules. This process occurs because atoms want to achieve a stable electron configuration. One of the most common types of chemical bonds is the covalent bond. In this explanation, we will explore covalent bonding in detail using simple language and lots of examples to help you understand. By the end of this lesson, you should have a very clear idea about what covalent bonds are, how they are formed, and why they are essential to life as we know it.

What is a covalent bond?

Covalent bonds are a type of chemical bond in which two atoms share a pair of electrons. These shared electrons allow each atom to achieve the electron configuration of a noble gas, which is usually a very stable arrangement. In most cases, covalent bonds form between non-metal atoms with similar electronegativities.

Understanding electron sharing

Atoms have electrons arranged in energy levels or shells around the nucleus. The outermost shell is known as the valence shell. Atoms want to fill their valence shells with the maximum number of electrons possible because a full valence shell is stable. For most of the first few rows of the periodic table, this means that the valence shell should have eight electrons, a rule known as the "octet rule."

In covalent bonding, atoms achieve a complete valence shell by sharing electrons. Let's consider an example using two hydrogen atoms:

H + H → H:H

In the diagram above, each hydrogen atom starts with one electron. By sharing these electrons (denoted as H:H), both hydrogen atoms can enjoy access to two electrons, completing their first and only shell.

Single, double, and triple bonds

Covalent bonds can involve one, two or three pairs of shared electrons, resulting in single, double and triple bonds, respectively. Here's how they work:

Single bonds

A single bond involves a pair of shared electrons. This is the simplest and most common type of covalent bond. For example, in a molecule of chlorine gas (Cl2), each chlorine atom shares one electron with the other:

Cl· + Cl → Cl:Cl
ChlorineChlorine

The line in the middle of the figure represents a shared electron pair or covalent bond.

Double bonds

A double bond is formed when two electron pairs are shared between two atoms. An example of this is the oxygen molecule (O2):

Oh Oh
HeyHey

The double line in the middle represents two shared electron pairs.

Triple bond

The triple bond involves three pairs of shared electrons, and is the strongest of the three types of covalent bonds. An example of a molecule with a triple bond is nitrogen gas (N2):

N:::N
NN

The three lines together represent three pairs of shared electrons.

Polar and nonpolar covalent bonds

Covalent bonds can be divided into two categories based on the sharing of electrons between atoms: polar and nonpolar covalent bonds.

Non-polar covalent bond

In a nonpolar covalent bond, the electrons are shared equally between the two atoms. This usually occurs between atoms of the same element or atoms with similar electronegativities. Examples include the hydrogen molecule (H2) and the oxygen molecule (O2).

Polar covalent bond

In a polar covalent bond the electrons are shared unequally. This means that one atom has a greater pull on the shared electrons. The atom with the greater pull is said to be more electronegative than the other. A common example of a polar covalent bond is found in the water (H2O) molecule:

Höh

In water, oxygen is more electronegative than hydrogen, which means it attracts shared electrons more strongly. This results in a slightly negative charge on the oxygen atom and a slightly positive charge on the hydrogen atom, creating a dipole moment.

Examples of covalent compounds

Covalent bonds form the basis of many different types of compounds. Here are some examples that show how versatile covalent bonds can be:

  • Carbon dioxide (CO2): This molecule has two double bonds between a carbon atom and two oxygen atoms.
    •     O=C=O
  • Methane (CH4): In methane, one carbon atom forms four single covalent bonds with four hydrogen atoms, making it a simple hydrocarbon.
    •     H
    ,
    HCH
    ,
    H
  • Ammonia (NH3): Ammonia is an example of a molecule where one nitrogen atom forms three single covalent bonds with three hydrogen atoms.
    •     H
    ,
    HNH

Importance of covalent bonds

Covalent bonds play a vital role in the chemistry of living organisms. They form the backbone of biological molecules such as proteins, nucleic acids, and carbohydrates. Without covalent bonds, the complex molecules necessary for life could not form or function.

For example, DNA, the molecule that carries genetic information in cells, is made up of covalent bonds that link sugars and phosphate groups together in a long chain that forms a helical structure. The ability of carbon atoms to form four covalent bonds makes it incredibly versatile in creating complex organic compounds.

Conclusion

Understanding covalent bonds is essential because it helps explain how atoms come together to form the different molecules that make up everything around us. From the water we drink, to the air we breathe, and to the cells in our bodies, covalent bonds are present everywhere, holding atoms together in stable, predictable ways. By sharing electrons, atoms can achieve a full outer shell, thereby achieving stability. The formation of single, double, and triple bonds gives molecules different properties, which affect the way they interact in chemical reactions. It's also important to know the difference between polar and nonpolar covalent bonds, because this affects molecule interactions, solubility, melting and boiling points, and electrical conductivity.

This comprehensive understanding of covalent bonds is important for further studies in chemistry and biology, and it lays the groundwork for in-depth study of more complex chemical behaviors and interactions in the future.


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Ionic bond
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Covalent bond

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