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 → Periodic Table and Chemical Trends ↓


History and Development of the Periodic Table


The periodic table is an important tool in chemistry that helps scientists understand the properties of elements and predict how they will behave in chemical reactions. Over time, the periodic table has evolved from a simple list of elements to a complex grid that organizes elements based on their atomic numbers and properties.

Initial discoveries

Before the periodic table was created, chemists knew about some elements. They discovered elements like gold, silver, and copper, which were used for coins, jewelry, and tools. As time went on, chemists began to discover more elements and tried to organize them in some logical way.

Birth of the modern periodic table

The modern periodic table was developed over many years with contributions from many scientists. The most notable of these contributions were from Russian chemist Dmitry Mendeleev and German chemist Lothar Meyer. Both worked independently on organizing the elements in the late 19th century.

Contribution of Dmitry Mendeleev

Dmitri Mendeleev is often credited with creating the first version of the periodic table in 1869. Mendeleev arranged the elements according to their atomic masses. He noticed that certain properties repeated periodically. His table left room for undiscovered elements, and he even predicted the properties of these elements based on the patterns he observed.

       H Lee B BCNOF
       NaMgAlSiPsClAr
       K ca br cr
       RB SR i XE
       CS Ba AT RN

Note: Some elements are missing in Mendeleev's table because they have not been discovered yet.

Acceptance and amendments

Mendeleev's table was groundbreaking because he made predictions about unknown elements. However, as new data emerged, it became clear that arranging the elements based solely on atomic mass was not entirely accurate. This led to several revisions over the years.

Contribution of Henry Moseley

Henry Moseley, an English physicist, made an important change to the periodic table. In 1913, he determined that the properties of the elements could be better predicted when they were arranged by their atomic number rather than atomic mass. The atomic number is the number of protons in the nucleus of an atom. Moseley's work corrected inconsistencies in the relative atomic weight order and refined the table layout.

      H2O
      by Lee B. BCNOF
      NaMgAlSiPsClAr
      K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br K

Modern periodic table

The modern periodic table is arranged according to increasing atomic number from left to right and top to bottom. Elements are also grouped based on similar properties. The rows of the periodic table are called periods, and the columns are known as groups or families.

The periodic table helps scientists quickly find an element and understand its properties. Let's take a look at some important aspects of its modern structure:

Periods and groups

In the periodic table, each row is called a period. As you move from left to right across a period, the chemical properties of elements change due to the increasing number of valence electrons. The columns are known as groups, and the elements in a group share chemical and physical properties. This is because they have the same number of electrons in their outer shell.

      
        
        H

        
        He

        
        Took

        
        Happen

        
        
        group 1
        period 1

In this view, the first group can be seen vertically and the first period horizontally.

Transition metal

The wide block in the center of the periodic table represents the transition metals. These elements have special properties because they can lose different numbers of electrons, giving them several oxidation states.

      
        
        t

        
        V

        
        Ten million

This group of elements is known to conduct electricity and be malleable and ductile.

Periodic trends

The periodic table not only helps us classify elements but also allows us to observe trends. Understanding these trends is important for predicting the behavior and properties of elements. Some of the primary trends include electronegativities, atomic radius, and ionization energy.

Electronegativity

Electronegativity refers to the ability of an atom to attract electrons in a chemical bond. Generally, electronegativities increase from left to right across a period and decrease from top to bottom across a group. Fluorine (F) is the most electronegative element.

      
        
        F

        
        Chlorine

In this view, fluorine is shown at the top, with its electronegativities increasing to the right and decreasing down the column.

Atomic radius

The atomic radius is the size of an atom. As you move across a period, the size of the atom decreases because electrons are pulled closer to the nucleus due to the increasing positive charge. As you move down a group, the size of the atom increases due to the addition of electron shells.

      
        
        No

        
        Chlorine

In this figure, the circle representing the sodium (Na) atom is larger than the circle representing the chlorine (Cl) atom.

Ionization energy

Ionization energy is the amount of energy required to remove an electron from an atom. Ionization energy increases from left to right across a period and decreases down a group. The highest ionization energies are found in noble gases.

      
        
        by

        
        AR
        
        
        Sl

This bar representation of ionization energy shows a general increase across a period in the noble gases such as neon (Ne), argon (Ar), and krypton (Kr).

Importance of periodic table

The periodic table is important because it organizes a vast amount of information about the chemical elements, helping scientists understand similarities and predict how different elements will react with each other. It is a tool that conveys a lot of information about the elements in a simple, visual way.

As new elements have been discovered, they have been added to the periodic table, often fitting predictions of the table's structure. This highlights the inherent consistency and predictive power of the periodic table as a scientific tool. Understanding the periodic table is fundamental to the study and practice of chemistry, and its development is a milestone in our understanding of the natural world.

The periodic table is an ongoing project. It adjusts with advancements in technology and discoveries, continuing to be relevant in helping scientists uncover the secrets of the elements.


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History and Development of the Periodic Table

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