- Mendeleev corrected atomic masses to correctly place elements.
- He predicted new elements like Sc, Ga, and Ge with correct properties.
- He later added a zero group for noble gases.
- Co and Ni have similar masses, which can cause confusion about their order.
- Isotopes couldn’t be placed due to different masses.
- Atomic mass gaps are uneven, so new elements couldn’t be predicted.
- Hydrogen's position is unclear—it’s like both alkali metals and halogens.
Topics
Gravitation
- Concept of Gravitation
- Force and Motion
- Centripetal Force
- Kepler’s Laws
- Law of Orbit or Kepler's First Law
- Law of Areas or Kepler's Second Law
- Law of Periods or Kepler's Third Law
- Newton's Universal Law of Gravitation
- Uniform Circular Motion (UCM)
- Earth’s Gravitational Force
- Earth’s Gravitational Acceleration
- Mass and Weight
- Gravitational Waves
- Free Fall
- Gravitational Potential Energy
- Escape Velocity
- Weightlessness in Space
Periodic Classification of Elements
- Classification of Elements
- Dobereiner’s Triads
- Newland's Law of Octaves
- Mendeleev’s Periodic Table
- Insights into Mendeleev’s Periodic Table
- Modern Periodic Law
- The Modern Periodic Table
- Structure of the Modern Periodic Table
- Modern Periodic Table and Electronic Configuration of Elements
- Groups and Electronic Configuration
- Periods and Electronic Configuration
- Periodic Trends in the Modern Periodic Table
- Atomic Size
- Metallic and Non-metallic Characters
- Gradation in Halogen Family
Chemical Reactions and Equations
- Chemical Reaction
- Chemical Equations
- Balancing Chemical Equation
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Endothermic and Exothermic Processes
- Rate of Chemical Reaction
- Factors Affecting the Rate of a Chemical Reaction
- Chemical Properties of Carbon Compounds > Oxidation
- Chemical Properties of Carbon Compounds > Reduction
- Corrosion of Metals
- Rancidity
Effects of Electric Current
- Electric Circuit
- Heating Effect of Electric Current
- Magnetic Effect of Electric Current
- Right-hand Thumb Rule
- Applications of Biot-Savart's Law > Magnetic Field at the Centre of a Circular Loop
- Applications of Ampere’s Circuital Law > Magnetic Field of a Long Straight Solenoid
- Force on a Current Carrying Conductor in a Magnetic Field
- Fleming’s Left Hand Rule
- Electric Motor
- Electromagnetic Induction
- Galvanometer
- Faraday's Laws of Electromagnetic Induction
- Fleming’s Right Hand Rule
- Alternating current (AC) and Direct Current (DC)
- Electric Generator
Heat
Refraction of Light
Lenses
- Concept of Lenses
- Images Formed by Convex Lenses
- Images Formed by Concave Lenses
- Sign Convention
- Lens Formula
- Magnification
- Power of a Lens
- Combination of Lenses
- The Human Eye
- Defects of Vision and Their Corrections > Myopia
- Defects of Vision and Their Corrections > Hypermetropia
- Defects of Vision and Their Corrections > Presbyopia
- Apparent Size of an Object
- Use of Concave Lenses
- Use of Convex Lenses
- Persistence of Vision
Metallurgy
- Physical Properties of Metals
- Physical Properties of Non-metal
- Chemical Properties of Metal
- Reactions of Metals
- Reactivity Series of Metals
- Chemical Properties of Non-metal
- Ionic Compounds
- Metallurgy
- Basic Principles of Metallurgy > Concentration of Ores
- Basic Principles of Metallurgy > Extraction of Metals
- Basic Principles of Metallurgy > Refining of Metals
- Corrosion of Metals
- Prevention of Corrosion
Carbon Compounds
- Bonds in Carbon Compounds
- Carbon: A Versatile Element
- Hydrocarbons
- Straight chains, Branched chains, and Rings of Carbon atoms
- Functional Groups in Carbon Compounds
- Homologous Series
- Nomenclature
- Chemical Properties of Carbon Compounds > Combustion
- Chemical Properties of Carbon Compounds > Oxidation
- Chemical Properties of Carbon Compounds > Addition Reaction
- Chemical Properties of Carbon Compounds > Substitution Reaction
- Ethanol
- Ethanoic Acid
- Macromolecules and Polymers
Space Missions
School of Elements
The Magic of Chemical Reactions
- Chemical Equations
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Chemical Properties of Carbon Compounds > Oxidation
- Types of Double Displacement: Neutralization Reaction
The Acid Base Chemistry
- Properties of Acids > Physical Properties
- The pH Scale
- Acids, Bases and Their Reactivity
- Acid or a Base in a Water Solution
- Preparation and Uses of Baking Soda
- Preparation and Uses of Bleaching Powder
- Preparation and Uses of Washing Soda
- Preparation and Uses of Plaster of Paris
- Chemicals from Common Salt - Soap as a Salt
The Electric Spark
All about Electromagnetism
- Magnetic force
- The Bar Magnet
- Right-hand Thumb Rule
- Applications of Biot-Savart's Law > Magnetic Field at the Centre of a Circular Loop
- Applications of Ampere’s Circuital Law > Magnetic Field of a Long Straight Solenoid
- Force on a Current Carrying Conductor in a Magnetic Field
- Electric Motor
- Electromagnetic Induction
- A.C. Generator
- Simple D.C. Motor
- Household Electrical Circuits
Wonders of Light 1
Wonders of Light 2
Striving for better Environment 1
- Abatement of Pollution
- Sustainable Use of Resources
- Key Points: Insights into Mendeleev's Periodic Table
Maharashtra State Board: Class 10
Key Points: Insights into Mendeleev’s Periodic Table
Maharashtra State Board: Class 10
Merits:
Science is progressive, allowing revisions based on new discoveries, as seen in Mendeleev’s Periodic Table. While arranging elements by atomic mass, Mendeleev considered that knowledge might change over time.
- Atomic masses were corrected for better placement. Example: Beryllium’s atomic mass was changed from 14.09 to 9.4, placing it before boron.
- Vacant spaces were left for undiscovered elements, predicting their properties. Example:
- Eka-boron → Scandium (Sc)
- Eka-aluminum → Gallium (Ga)
- Eka-silicon → Germanium (Ge)
Property Eka-aluminum (E) (Mendeleev’s prediction) Gallium (Ga) (actual) 1. Atomic mass 68 69.7 2. Density (g/cm³) 5.9 5.94 3. Melting point (°C) Low 30.2 4. Formula of chloride ECl₃ GaCl₃ 5. Formula of oxide E₂O₃ Ga₂O₃ 6. Nature of oxide Amphoteric oxide Amphoteric oxide
- Predicted properties matched actual properties, proving the periodic table’s accuracy.
- Noble gases were accommodated in a new ‘zero group’ without disturbing the table after their discovery.
Maharashtra State Board: Class 10
Demerits:
- Cobalt (Co) and nickel (Ni) have nearly the same atomic mass, causing ambiguity in their placement.
- Isotopes posed a challenge since they have the same chemical properties but different atomic masses.
- Irregular atomic mass increases made it difficult to predict the number of elements between heavy elements.
- The position of hydrogen was unclear because it shares properties with both:
- Alkali metals (Group I): Forms compounds like HCl (similar to NaCl) and H₂O (similar to Na₂O).
- Halogens (Group VII): Forms compounds like NaH (similar to NaCl) and CH₄ (similar to CCl₄).
Similarity in hydrogen and alkali metals:
| Compounds of H | Compounds of Na |
|---|---|
| HCl | NaCl |
| H₂O | Na₂O |
| H₂S | Na₂S |
Similarity in hydrogen and halogens:
| Element (Molecular Formula) | Compounds with Metals | Compounds with Nonmetals |
|---|---|---|
| H₂ | NaH | CH₄ |
| Cl₂ | NaCl | CCl₄ |
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Related QuestionsVIEW ALL [46]
Match the columns.
| Column A | Column B |
| 1) Eka-aluminium | a) Scandium |
| 2) Eka-Silicon | b) Gallium |
| 3) Eka- boron | c) Germanium |
| d) Beryllium |
