Grade 8
  1. Introduction to Chemistry  1.1. Nature and scope of chemistry  1.2. Importance of chemistry in daily life  1.3. Chemistry and its relation with other sciences  1.4. The role of chemistry in industry, medicine and the environment  1.5. Scientific investigation and experimental methods in chemistry
  2. Matter and its properties  2.1. Definition and classification of matter  2.2. Physical and chemical properties of matter  2.3. Law of conservation of matter  2.4. Extensive and Intensive Properties of Matter  2.5. Kinetic molecular theory of matter  2.6. States of matter: solids, liquids, gases, plasmas, and Bose-Einstein condensates  2.7. Changes in state and energy are involved  2.8. Diffusion and Brownian motion
  3. Elements, Compounds, and Mixtures  3.1. Definition and differences between elements, compounds, and mixtures  3.2. Atomic Structure and Atomic Number  3.3. Chemical symbols and formulas  3.4. Trends in the Periodic Table (Groups and Periods)  3.5. Classification of Elements: Metals, Nonmetals and Metalloids  3.6. Rare Earth Elements and Transition Metals  3.7. Types of mixtures: homogeneous and heterogeneous  3.8. Separation of Mixtures Using Physical and Chemical Methods
  4. Separation Techniques  4.1. Filtration, Sedimentation and Decantation  4.2. Evaporation and crystallization  4.3. Distillation and Fractional Distillation  4.4. Chromatography and its applications  4.5. Sublimation in the purification of compounds  4.6. The role of centrifugation in biochemical processes
  5. Atomic Structure  5.1. Dalton's atomic theory  5.2. Structure of the atom: protons, neutrons and electrons  5.3. Bohr's atomic model  5.4. Introduction to Quantum Mechanical Model  5.5. Electron Configuration and Energy Levels  5.6. Excitation and emission spectra  5.7. Isotopes and their applications
  6. Periodic Table and Chemical Trends  6.1. History and Development of the Periodic Table  6.2. Modern periodic law  6.3. Periodicity and trends in atomic and ionic sizes  6.4. Ionization Energy, Electron Affinity and Electronegativity  6.5. Introduction to Lanthanides and Actinides  6.6. Application of periodic trends in chemistry
  7. Chemical Bonding and Molecular Structure  7.1. Types of chemical bonds: ionic, covalent and metallic bonds  7.3. Polar and Nonpolar Molecules  7.4. Hydrogen bonding and its applications  7.5. Intermolecular forces: dipole-dipole, London dispersion force
  8. Chemical Reactions and Stoichiometry  8.1. Chemical Equations and Balance  8.2. Types of Chemical Reactions: Combination, Decomposition, Displacement and Redox  8.3. Introduction to stoichiometry and the mole concept  8.4. Limiting reactant in chemical equations  8.5. Reaction rate, catalyst, and factors affecting reaction rate
  9. Acids, Bases and Salts  9.1. Definition and Properties of Acids and Bases  9.2. Strong vs. Weak Acids and Bases  9.3. pH Scale and pH Calculation  9.4. Neutralization reactions  9.5. Buffer solutions and their importance  9.6. Applications of Acids, Bases and Salts in Daily Life
  10. Solutions and Solubility  10.1. Definition of Solution, Solute, and Solvent  10.2. Factors Affecting Solubility  10.3. Concentration units: molarity and molality  10.4. Saturated, unsaturated and supersaturated solutions  10.5. Concept of osmosis and reverse osmosis  10.6. Concentrative properties of solutions
  11. Gases and Gas Laws  11.1. Properties of gases  11.2. Introduction to Ideal and Real Gases  11.3. Boyle's Law, Charles' Law and Avogadro's Law  11.4. Ideal Gas Equation and Its Applications  11.5. Application of Gas Laws in Real Life
  12. Thermochemistry and energy transformation  12.1. Energy in Chemical Reactions  12.2. Exothermic vs. Endothermic Reactions  12.3. Heat and Enthalpy Changes  12.4. Calorimetry and heat transfer in reactions
  13. Metals and Nonmetals  13.1. Physical and Chemical Properties of Metals and Nonmetals  13.2. Reactivity Series of Metals  13.3. Corrosion and its prevention  13.4. Extraction of metals from ores  13.5. Uses of metals and non-metals in daily life
  14. Introduction to Organic Chemistry  14.1. Characteristics of carbon and organic compounds  14.2. Functional groups and their importance  14.3. Simple Hydrocarbons: Alkenes, Alkenes and Alkynes  14.4. Isomerism in organic compounds  14.5. Introduction to polymers and their uses
  15. Environmental Chemistry and Sustainability  15.1. Green Chemistry Principles  15.2. Effects of Chemical Pollution on Ecosystems  15.3. Acid rain and its effects  15.4. Ozone layer depletion and global warming  15.5. Waste Management and Recycling in Chemistry

Grade 8 → Elements, Compounds, and Mixtures ↓


Classification of Elements: Metals, Nonmetals and Metalloids


Introduction

The periodic table is a systematic chart of the elements and it helps us understand the properties and behaviour of different atoms. The elements in the periodic table are classified into three main categories: metals, nonmetals, and metalloids. Each of these categories has different properties and uses, and understanding them is important for studying chemistry. Let's explore these classifications in detail by examining their physical properties, chemical properties, and uses.

Metals

Most elements in the periodic table are metals. Metals are typically shiny, good conductors of heat and electricity, and malleable and ductile. Here we take a look at some common properties of metals:

Physical properties of metals

  • Lustre: Metals look shiny.
  • Malleability: Metals can be beaten into thin sheets. For example, gold can be made into very thin sheets called gold leaf.
  • Ductility: Metals can be stretched into wires. Copper is a common metal used for electrical wires.
  • Conductivity: Metals conduct electricity and heat well. This is why they are used in electrical wiring and cookware.

Chemical properties of metals

  • Reactivity: Metals like sodium and potassium are highly reactive. Other metals like gold and platinum are less reactive.
  • Formation of compounds: Metals often form ionic compounds. For example, sodium (Na) reacts with chlorine (Cl) to form sodium chloride (NaCl).

Examples of metals

Element Sign General Use
Iron Fe Construction, Manufacture of automobiles
Gold Au Jewellery, Electronics
Copper Cu Electrical wiring, plumbing
Metal bars

Visual example of metals

The illustration of metal rods shows the characteristic metallic lustre and good conductor nature of metals.

Nonmetals

Nonmetals are few in number but are essential to life. Nonmetals have different properties than metals and are very important in both organic and inorganic chemistry.

Physical properties of nonmetals

  • Appearance: Non-metals do not have the lustre of metals. They may be colourless like nitrogen or coloured like iodine.
  • Brittleness: Non-metals are brittle if they are solid, like sulphur.
  • Insulators: These are generally poor conductors of heat and electricity, making them good insulators.

Chemical properties of nonmetals

  • High electronegativities: Nonmetals generally have high electronegativities and are more likely to gain electrons in reactions.
  • Formation of covalent bonds: They often form covalent compounds. For example, hydrogen (H) and oxygen (O) combine to form water (H2O).

Examples of nonmetals

Element Sign General Use
Oxygen O Respiration, steel production
Nitrogen N Fertilizer, Refrigeration
Carbon C Fuel, structural materials
Nonmetal atoms

Visual example of nonmetals

The circle represents a nonmetal atom, symbolizing the general property of nonmetals to form molecules and compounds.

Metalloids

The properties of metalloids are intermediate between metals and non-metals. They are located on a stepped line on the periodic table.

Properties of metalloids

  • Appearance: Metalloids may be lustrous or dull.
  • Semiconductors: Metalloids such as silicon are semiconductors, meaning they can conduct electricity better than nonmetals, but not as well as metals.
  • Intermediate Reactivity: They show intermediate reactivity and are used in various applications.

Chemical behaviour of metalloids

  • Alloying: Metalloids can form alloys with metals. For example, silicon is used to make silicon steel.
  • Variable reactivities: Their reactivities can vary widely - Boron forms compounds with hydrogen, such as borane (B2H6).

Examples of metalloids

Element Sign General Use
Silicon Si Glass, electronics
Boron B Ceramics, detergents
Metalloid Crystals

Visual example of metalloids

This polygonal shape represents a metalloid crystal, indicating that they can form unique structures, especially in electronics.

Conclusion

Understanding the classification of elements into metals, nonmetals, and metalloids helps us understand the wide range of materials available in the world. Metals are important in construction and infrastructure due to their strength and conductivity. Nonmetals, despite being poor conductors, play important roles in biological systems and industrial applications. With their unique properties, metalloids bridge the gap between metals and nonmetals, especially in technology. Recognizing these categories and their characteristics allows exploring their applications in science and industry.


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Classification of Elements: Metals, Nonmetals and Metalloids

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