Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Atomic Structure ↓


Subatomic particles


At the core of all chemistry lies the concept of the atom. The atom is the basic building block of matter, and understanding its structure is crucial to understanding how substances interact at the molecular level. In this article, we will learn in detail about the three fundamental subatomic particles that make up an atom - protons, neutrons, and electrons.

These particles are the smallest units of matter that retain the identity of the element. Although they are incredibly small, understanding their properties and interactions provides insight into the diverse world of chemistry.

Atom: structure and assembly

An atom is made up of three main particles: protons, neutrons and electrons. These particles are arranged in such a way that a structure like a miniature solar system is formed. At the center of the atom is the nucleus, which contains both protons and neutrons. Surrounding the nucleus is a cloud of electrons. Each component of the atom plays an important role in determining the properties and behavior of the element.

Proton

Protons are positively charged particles found in the nucleus of an atom. The charge of a proton is +1. The number of protons in the nucleus of an atom is called the atomic number and it defines the identity of an element. For example, an element with one proton is hydrogen, two protons form helium and six protons form carbon.

Here's a simplified diagram of a proton: P +

The protons are held together in the nucleus by a strong force known as the nuclear force. Despite their positive charge, which causes them to repel one another, the nuclear force is strong enough to hold the nucleus together.

Neutron

Neutrons are neutral particles, meaning they have no electrical charge. Like protons, they reside in the nucleus of an atom. Atoms of the same element can have different numbers of neutrons, forming isotopes. For example, carbon can exist as carbon-12 with six neutrons or carbon-14 with eight neutrons.

Here's a simplified diagram of a neutron: N

Neutrons play an important role in keeping the nucleus stable. Without neutrons, the repulsion force between the positively charged protons would tear the nucleus apart.

Electrons

Electrons are negatively charged particles that orbit the nucleus in specific regions called electron shells or energy levels. Electrons have a charge of -1 and have a very small mass compared to protons and neutrons.

Here's a simplified diagram of an electron: E -

The arrangement of electrons significantly affects the chemical properties of an atom. Electrons are at different energy levels, and the number of electrons in the outermost shell, known as valence electrons, determines how atoms interact and bond with each other.

Interaction of subatomic particles

Understanding the interactions between protons, neutrons, and electrons is important to understanding atomic structure. The balance of these particles determines the overall charge and stability of an atom.

Atoms are usually electrically neutral because the number of protons (positive charge) is equal to the number of electrons (negative charge). However, when an atom gains or loses electrons, it becomes an ion. Ions can be positively charged (cations) when they lose electrons, or negatively charged (anions) when they gain electrons.

Example: sodium atom

Sodium is a chemical element with the symbol Na and atomic number 11. A neutral sodium atom has 11 protons, 12 neutrons, and 11 electrons. 

Protons: 11
Neutrons: 12
Electrons: 11

When sodium loses an electron, it becomes a sodium ion (Na +). The loss of an electron leaves it with one more proton than electrons, giving the ion a positive charge.

Example: chlorine atom

Chlorine is a chemical element with the symbol Cl and atomic number 17. A neutral chlorine atom has 17 protons, 18 neutrons, and 17 electrons. 

Protons: 17
Neutrons: 18
Electrons: 17

When chlorine gains an extra electron, it becomes a negatively charged chloride ion (Cl−).

Importance of subatomic particles in chemistry

The arrangement and interactions of subatomic particles form the diverse world of chemistry. Some of the important concepts arising from these interactions are as follows:

  • Atomic number: Defined by the number of protons in an atom, the atomic number is important for identifying the element. It organizes the periodic table and determines the element's chemical properties.
  • Mass number: The sum of the protons and neutrons in the nucleus of an atom gives the mass number, which is used to differentiate isotopes.
  • Isotopes: Types of elements that have the same number of protons but different numbers of neutrons. Isotopes can exhibit different nuclear properties and are used in a variety of applications, such as carbon dating.
  • Ions: Charged particles formed when atoms gain or lose electrons. Ions play an important role in chemical reactions, especially reactions involving ionic compounds.
  • Chemical bond: The interaction of electrons, especially valence electrons, leads to the formation of chemical bonds, such as covalent and ionic bonds, which hold atoms together in molecules and compounds.

Conclusion

Understanding subatomic particles is essential to understanding the complexities of chemistry. Protons, neutrons, and electrons form the foundation of atomic structure, affecting everything from the identity of elements to the behavior of atoms in chemical reactions. By studying these particles, we further our understanding of the natural world and its vast range of substances.

With this knowledge, students gain the ability to explore the fascinating world of chemistry, understanding the interactions that occur at the subatomic level that give rise to the rich diversity of substances and reactions in our universe.


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Subatomic particles

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