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 ↓


Properties of Ionic and Covalent Compounds


In the world of chemistry, it is interesting to understand how different atoms stick together to form compounds. The two main ways atoms bond are ionic and covalent bonds. Understanding the properties of ionic and covalent compounds helps us identify how they behave in different situations.

Ionic compounds

Ionic compounds are formed by the electrostatic attraction between positively and negatively charged ions. This occurs when one atom gives up one or more electrons, becoming a positively charged ion or cation, while the other atom gains those electrons, becoming a negatively charged ion or anion.

For example, when sodium (Na) and chlorine (Cl) combine to form sodium chloride (NaCl), sodium transfers one electron to chlorine, forming Na+ and Cl- ions:

Na → Na + + e -
Cl + e - → Cl -
Na + + Cl - → NaCl

Properties of ionic compounds

  • High melting and boiling point:
    Ionic compounds generally have high melting and boiling points because of the strong electrostatic forces between the ions, which require more energy to break down.
  • Solid at room temperature:
    At room temperature, most ionic compounds exist as solid crystalline structures.
  • Conductivity when dissolved in water:
    Ionic compounds can conduct electricity when dissolved in water because the ions are free to move and carry a charge.
  • Brittleness:
    Ionic compounds are often brittle. Their crystals can break easily, because when the ions move, the charges align to repel each other.
  • Solubility in water:
    Many ionic compounds are soluble in water, but this solubility can vary.

These properties can be visualized as follows:

ionic lattice Strong forces

Covalent compounds

On the other hand, covalent bonding occurs when two atoms share one or more electron pairs. This type of bond is typically formed between nonmetal atoms. The shared electrons allow each atom to achieve the electron configuration of the noble gases, thereby achieving stability.

One of the simplest examples is the bond in a hydrogen gas (H2) molecule:

h ⋯ h
H2 molecule

Properties of covalent compounds

  • Low melting and boiling point:
    Covalent compounds generally have lower melting and boiling points. Their intermolecular forces are weaker, requiring less energy to overcome.
  • Existing in various states:
    These compounds may be gases, liquids, or solids at room temperature.
  • Poor electrical conductivity:
    Covalent compounds are poor electrical conductors because they contain no free electrons or ions to transport electrical charge.
  • Slightly soluble in water:
    Unlike ionic compounds, they are less soluble in water, but can dissolve in nonpolar solvents.
  • Different types of formats:
    Covalent compounds can form complex shapes and structures, such as chains, rings, and networks.

An illustration showing a covalent bond:

Shared Electrons

Conclusion

In short, by knowing the way atoms bond and the properties of the resulting compound, scientists and students can predict and understand the behavior of substances under different conditions. Whether it is the high melting point of salt due to ionic bonds or the ability of sugar to dissolve in water due to covalent bonds, these characteristics are essential for the application of chemistry in real-world scenarios.


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Properties of Ionic and Covalent Compounds

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