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 → Atomic Structure ↓


Structure of the atom


The atom is the basic unit of matter consisting of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atom is the smallest unit of ordinary matter that makes up a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Below is a simple representation of an atomic structure with its components through a diagram.

Nucleus
(proton+neutron)

Atoms are composed mainly of three types of particles:

  • Protons: These are positively charged particles that reside in the nucleus of an atom. Each proton has a charge of +1. The number of protons determines the element. For example, hydrogen has 1 proton, carbon has 6, etc.
  • Neutrons: These particles have no charge (neutral) and are also located in the nucleus of the atom. Atoms of the same element can have different numbers of neutrons, forming different isotopes. Although neutrons do not affect the charge, they do increase the mass of the atom.
  • Electrons: Electrons are negatively charged particles (-1) located in the electron cloud surrounding the nucleus. They are in constant motion around the nucleus. Their arrangement in different energy levels (or shells) determines how atoms bond with each other.

The structure of an atom can be thought of as a miniature solar system, where the nucleus is like the sun, and the electrons are like the planets orbiting around it.

Protons, neutrons and electrons

Proton

Let's take a deeper look at protons. Since the atomic number defines an element, it is typically equal to the number of protons found in the nucleus. For example, calcium has an atomic number of 20, which means it has 20 protons.

Neutron

Neutrons look similar to protons, but they do not have an electrical charge. They are important in providing the weight that makes up the overall mass of an atom. Isotopes of an element differ due to differences in the number of neutrons they have. For example, carbon-12 and carbon-14 are both isotopes of carbon, but they differ in their number of neutrons.

Electrons

Electrons play a vital role in chemical reactions and bonding despite their small mass relative to protons and neutrons. They live in electron clouds around the nucleus, constantly moving around and occupying different energy levels. The behavior of electrons is described by quantum mechanics, which indicates the probability of finding an electron in any particular region.

Center

The nucleus is the heart of the atom, containing almost all of the atom's mass. It contains both protons and neutrons. The forces holding the nucleus together are called nuclear forces, which are far more powerful than the electromagnetic forces that repel the protons due to their positive charge. This incredible force ensures that the nucleus remains intact.

Electron cloud

Electrons exist in this vast space around the nucleus. They are not fixed in orbits like the planets in our solar system, but rather they exist in probability regions called orbitals. These regions tell where the electron is likely to be found.

Electron configuration

Electrons reside in different shells around the nucleus, occupying levels based on their energy. These layers are labeled K, L, M, N, etc., with the K shell being closest to the nucleus.

1st shell (K) can hold up to 2 electrons. 2nd shell (L) can hold up to 8 electrons. 3rd shell (M) can hold up to 18 electrons. 4th shell (N) can hold up to 32 electrons.

Understanding the electron configuration of an element reveals how it interacts and bonds with other elements. For example, sodium (Na) with atomic number 11 would have its electron configuration arranged as 2, 8, 1 in the K, L, and M shells, respectively.

Valence electrons

The outermost shell of an atom is important for its reactivity and ability to bond with other atoms. The electrons in this shell are called valence electrons. Atoms strive for stability by filling their outer shell, often achieving this by gaining, losing, or sharing electrons with other atoms. For example, sodium, which has one electron in its outer shell, loses that electron to achieve stability.

Periodic table and atomic structure

The periodic table serves as a roadmap that displays all known elements in a systematic way. It reveals important information about each element, such as its atomic number, which indicates the number of protons, and thus defines the element's identity. The table also organizes elements based on their electron configuration and shared properties, such as reactivity.

Matter and its states

All the physical matter around us, the environment and even our bodies are made up of atoms, which form different states of matter: solid, liquid, gas and plasma. Whenever we observe a change between these states, for example, melting, freezing or evaporation, the underlying atomic structure remains, the atoms simply rearrange or move differently.

Chemistry formulas: Visualizing atoms

In chemistry atoms are often represented by symbols, using formulas that show their interactions. For example, a water molecule is represented as:

H2O

This simple formula indicates that water consists of two hydrogen atoms bonded to one oxygen atom. Upon further examination of the water molecule, one can appreciate its unique properties, such as its state at room temperature, its ability to dissolve substances, and its role in life on Earth. Each property is related to the composition and structure of the atoms of the water molecule.

Conclusion

Understanding the structure of the atom establishes a basis for exploring more complex concepts in chemistry and physics. The protons, neutrons, and electrons of an atom govern not only the identity of an element but also its chemical behavior and interactions with other elements. This knowledge provides essential insights into the diversity of matter and the processes within our observable universe. Understanding atomic structure thus unravels the fundamental principles governing matter, life, and the universe itself.


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Structure of the atom

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