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 → Periodic table ↓


Trends in the Periodic Table


The periodic table is a chart that organizes the chemical elements based on their properties. It helps scientists and students understand the relationships between different elements and predict how they will behave. Let's explore the trends seen in the periodic table, focusing on the elements' properties and relationships with one another.

1. Introduction to the Periodic Table

The periodic table was first designed by Dmitri Mendeleev in 1869. It is arranged in rows called periods and columns called groups or families. The position of each element in the table can provide a lot of information about its size, energy, chemical reactivity, and more. Here, we'll explore several major trends that appear as we move across a period (from left to right) and a group (from top to bottom).

2. Atomic size

Atomic size refers to the distance from an atom's nucleus to its outermost electron shell. This distance affects how atoms interact with each other. Atomic size changes regularly as you move across periods and groups.

2.1 Trend over a period

The size of the atom decreases across a period. As new protons and electrons are added to the atom moving from left to right, the increased positive charge in the nucleus pulls the electrons closer, making the atom smaller.

Li > Be > B > C > N > O > F > Ne
Took Happen B C

2.2 Downward trend in the group

In a group, the size of the atom increases as we move down. This is because each element down the group has an extra electron shell compared to the element directly above it, which makes the atom larger.

H < Li < Na < K < Rb
H Took No K

3. Ionization energy

Ionization energy is the energy required to remove an electron from an atom in the gaseous state. Understanding this trend helps predict how easily an atom can form positive ions.

3.1 Trend over a period

Across a period, ionization energy generally increases. As the size of the atom decreases, electrons are held more tightly by the nucleus, requiring more energy to remove them.

Li < Be < B < C < N < O < F < Ne
Took Happen B

3.2 Downward trend in the group

Ionization energy decreases as we go down the group. Larger atomic sizes cause the outermost electrons to be farther from the nucleus, making them easier to remove using less energy.

He > Ne > Ar > Kr > Xe
He by AR

4. Electronegativity

Electronegativity is a measure of an atom's ability to attract electrons and bind them in chemical bonds. Elements with higher electronegativities will pull electrons toward themselves more strongly.

4.1 Trend over a period

Electronegativity increases as you move from left to right across a period. This is because atoms are smaller and closer to stabilizing their outer electron shell by attracting extra electrons.

Na < Mg < Al < Si < P < S < Cl
No Milligrams Al

4.2 Downward trend in the group

Electronegativity decreases as we go down a group. As the size of the atom increases, the pull exerted by the nucleus on the electrons becomes weaker.

F > Cl > Br > I
F Chlorine BR

5. Metallic and non-metallic character

The metallic character of an element is based on its ability to lose electrons and form positive ions. In contrast, the non-metallic character is based on the ability of an element to gain electrons.

5.1 Trend over a period

Across a period, metallic properties decrease, while nonmetallic properties increase. On the left side of a period, elements easily lose electrons (metals), and on the right side, they gain electrons (nonmetals).

Na > Mg > Al > Si > P > S > Cl
No Milligrams Al

5.2 Downward trend in the group

Metallic character increases going down the group because larger atoms lose electrons more easily. Non-metallic character decreases because atoms are less likely to gain additional electrons.

Li > K > Rb > Cs
Took K RB

6. Summary

Understanding the trends in the periodic table is important for predicting the chemical properties of elements. As students learn more about these trends, they can better understand how the elements interact in compounds and how they behave under different conditions.


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Trends in the Periodic Table

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