Chemical Reactions and Equations
- Chemical Equation
- Balancing Chemical Equation
- Types of Chemical Change or Chemical Reaction
- Direct Combination (or Synthesis) Reaction
- Decomposition Reactions
- Single Displacement Reactions
- Double Displacement Reaction
- Oxidation, Reduction and Redox Reactions
- Corrosion of Metals and Its Prevention
- Rancidity of Food and Its Prevention
Chemical Substances - Nature and Behaviour (Chemistry)
Acids, Bases and Salts
- Bases (Alkalis)
- Properties of Acids
- Properties of Bases (Alkalis)
- Acid or a Base in a Water Solution
- Similarities and Differences Between Acids and Bases
- Strength of Acidic or Basic Solutions
- Chemicals from Common Salt (Uses of Salt)
- Preparation and Uses of Sodium Hydroxide
- Preparation and Uses of Bleaching Powder
- Preparation and Uses of Baking Soda
- Preparation and Uses of Washing Soda
- Preparation and Uses of Plaster of Paris
World of Living (Biology)
Metals and Non Metals
- Types of Elements: Metals
- Physical Properties of Metals
- Chemical Properties of Metal
- Types of Elements: Non-metal
- Physical Properties of Non-metal
- Chemical Properties of Non-metal
- Electrovalent (or Ionic) Bond
- Reactivity Series of Metals
- Extraction of Metals
- Refining of Metals
- Corrosion of Metals and Its Prevention
- The Covalent Bond
Natural Phenomena (Physics)
Effects of Current (Physics)
Carbon and its Compounds
- Carbon: a Versatile Element
- The Covalent Bond
- Saturated and Unsaturated Carbon Compounds
- Allotropy and Allotropes of Carbon
- Crystalline Allotropes of Carbon: Diamond
- Crystalline Allotropes of Carbon: Graphite
- Crystalline Allotropes of Carbon: Fullerene
- Chains, Branches and Rings of Carbon Compound
- Functional Groups in Carbon Compounds
- Homologous Series of Carbon Compound
- Nomenclature of Organic Compounds (IUPAC)
- Chemical Properties of Carbon Compound
- Ethanoic Acid
- Cleansing Action of Soap
Periodic Classification of Elements
- History of Periodic Table: Early Attempts at the Classification of Elements
- Dobereiner’s Triads
- Newland's Law of Octaves
- Mendeleev’s Periodic Table
- Merits and Demerits of Mendeleev’s Periodic Table
- The Modern Periodic Table
- Periodic Properties
- Periodic Properties: Valency
- Periodic Properties: Atomic Radius Or Atomic Size
- Periodic Properties: Metallic Character
- Periodic Properties: Non-metallic Character
- Living Organisms and Life Processes
- Nutrients and Nutrition
- Mode of Nutrition in Plant
- Autotrophic Nutrition
- Heterotrophic Nutrition
- Different Ways of Taking Food
- Human Digestive System
- The Mouth and Buccal Cavity
- The Teeth and Its Structure
- The Salivary Glands
- Swallowing and Peristalsis
- The Food Pipe/Oesophagus
- The Stomach
- The Small Intestine
- Absorption of Food
- The Large Intestine
- Assimilation of Food
- Respiration in Organisms
- Breathing in Other Animals
- Types of Respiration: Aerobic and Anaerobic Respiration
- Human Respiratory System
- Plasma: The Liquid Portion of Blood
- Composition of Blood: Red Blood Cells (Erythrocytes)
- Composition of Blood: White Blood Cells (Leukocytes)
- Composition of Blood: Blood Platelets (Thrombocytes)
- Blood Circulatory System in Human
- Human Heart
- Blood Vessels – Arteries, Veins, and Capillaries
- Circulation of Blood in the Heart (Functioning of Heart)
- Types of Blood Circulation
- Heart Beat - Heart Sounds "LUBB" and "DUP"
- Function of Platelets - Clotting of Blood (Coagulation)
- Lymph and Lymphatic System
- Blood Pressure (B.P.)
- Transportation of Water and Food in Plants
- Water and Mineral Absorption by Root
- Translocation of Water (Ascent of Sap)
- Translocation of Mineral Ions
- Transport of Food
- Excretion: Substances to Be Eliminated
- Human Excretory System
- Function of the Kidney - “Production of Urine”
- Excretion in Plants
Control and Co-ordination
- Control and Co-ordination in Animals
- Human Nervous System
- Neuron (Or Nerve Cell) and Its Types
- Structure of the Neuron
- Nerve Fibres
- Major Division of the Nervous System
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- The Human Brain
- Central Nervous System (CNS): Structure of Human Brain
- Reflex and Reflex Action
- Nervous Pathways in Reflexes
- Reflex Arc
- Co-ordination in Plant: Tropism in Plants
- Plant Hormones
- Types of Plant Hormones: Auxins
- Types of Plant Hormones: Gibberellins
- Types of Plant Hormones: Ethylene
- Types of Plant Hormones: Cytokinins
- Types of Plant Hormones: Abscisic Acid (ABA)
- Types of Plant Hormones: Ethylene
- Hormones in Animals
- Human Endocrine System
- Pituitary Gland or Hypophysis Gland
- Thyroid Gland
- Parathyroid Gland
- Pancreas (Islets of Langerhans)
- Adrenal Gland (Suprarenal Gland)
- Reproductive Glands (Gonads)
- Thymus Gland
How do Organisms Reproduce?
- Accumulation of Variation During Reproduction
- Reproduction in Plant
- Mode of Reproduction in Plant
- Asexual Reproduction in Plant
- Method of Natural Vegetative Propagation
- Sexual Reproduction in Flowering Plants
- Sexual Reproduction in Animals
- Human Reproductive System
- Male Reproductive System
- Female Reproductive System
- Menstrual Cycle (Ovarian Cycle)
- Reproductive Health
- Sexually Transmitted Diseases (STD)
Heredity and Evolution
- Accumulation of Variation During Reproduction
- Gregor Johann Mendel – Father of Genetics
- Monohybrid Cross - Inheritance of One Gene
- Dihybrid Cross - Inheritance Two Genes and Law of Independent Assortment
- Mendel’s Laws of Inheritance
- Sex Determination
- Theories of Evolution: Lamarckism
- Theories of Evolution: Darwinism or Theory of Natural Selection
- Origin of Life (Theories)
- Evolution and Classiffication
- Evidence of Organic Evolution
- Evolution by Stages
- Human Evolution
Light - Reflection and Refraction
- Reflection of Light
- Law of Reflection of Light
- Mirrors and Its Types
- Plane Mirror and Reflection
- Spherical Mirrors
- Rules for the Construction of Image Formed by a Spherical Mirror
- Images Formed by Spherical Mirrors
- Concave Mirror
- Image Formation by Concave Mirror
- Convex Mirror
- Image Formation by Convex Mirror
- Sign Convention for Reflection by Spherical Mirrors
- Mirror equation/Formula
- Linear Magnification (M) Due to Spherical Mirrors
- Refraction of Light
- Refraction of Light Through a Rectangular Glass Slab
- Law of Refraction of Light
- Refractive Index
- Spherical Lens
- Images Formed by Sperical Lenses
- Guideline for Image Formation Due to Refraction Through a Convex and Concave Lens
- Concave Lens
- Images Formed Due to Refraction Through a Concave Lens
- Convex Lens
- Images Formed Due to Refraction Through a Convex Lens
- Sign Convention for Spherical Lenses
- Lens Formula
- Magnification Due to Spherical Lenses
- Power of a Lens
The Human Eye and the Colourful World
- Human Eye: Structure of the Eye
- Working of the Human Eye
- Eye Defect and Its Correction: Myopia Or Near-sightedness
- Eye Defect and its correction: Hypermetropia or far-sightedness
- Eye Defect and Its Correction: Presbyopia
- Care of the Eyes
- Refraction of Light Through a Prism
- Concept of Prism
- Dispersion of Light Through Prism and Formation of Spectrum
- Atmospheric Refraction
- Application of Atmospheric Refraction
- Scattering of Light and Its Types
- Applications of Scattering of Light
- Electric Current
- Electric Circuit
- Electric Potential (Electrostatic Potential) and Potential Difference
- Symbols and Functions of Various Components of an Electric Circuits
- Ohm's Law
- Factors Affecting the Resistance of a Conductor
- Electrical Resistivity and Electrical Conductivity
- Resistors in Series
- Resistances in Parallel
- Effects of Electric Current
- Heating Effect of Electric Current
- Electrical Power
Magnetic Effects of Electric Current
- Magnetic Effect of Electric Current
- Magnetic Field
- Magnetic Field Lines
- Magnetic Field Due to a Current Carrying Straight Conductor
- Rule to Find the Direction of Magnetic Field
- Magnetic Field Due to Current in a Loop (Or Circular Coil)
- Magnetic Field Due to a Current Carving Cylindrical Coil (or Solenoid)
- Force on a Current Carrying Conductor in a Magnetic Field
- Electric Motor
- Electromagnetic Induction
- Faraday's Laws of Electromagnetic Induction
- Alternating Current (A.C.) Generator
- Direct Current Motor
- Household Electrical Circuits
- Distinction Between an A.C. Generator and D.C. Motor
- Types of current: Alternating Current (A.C.) and Direct Current (D.C.)
Sources of Energy
- Source of Energy
- Conventional Sources of Energy and Non-conventional Sources of Energy
- Fossil Fuels
- Heat Energy (Thermal Energy)
- Hydroelectric Energy
- Wind Energy
- Solar Energy
- Solar Energy Devices
- Energy from the Sea
- Nuclear Energy
- Nuclear Fission
- Different Forms of Energy
- Environmental Consequences
- How Long Will an Energy Source Last Us?
Sustainable Management of Natural Resources
- Sustainability of Natural Resources
- Case Study: Ganga Pollution and Ganga Action Plan
- Solid Waste Management
- Five R’s of Waste Management
- Conservation and Judicious Use of Resources
- Forests: Our Lifeline
- Stakeholders of Forest
- Conservation of Forest
- Conservation of Wildlife
- Water Management (Conservation of Water)
- Fresh Water Management
- Non-crystalline/Amorphous Forms: Coal
- Conservation of Coal, Petroleum, and Natural Resources
- Overview of Natural Resource Management
The Modern Periodic Table has 18 vertical columns known as ‘groups’ and 7 horizontal rows known as ‘periods’.
You will find that all these elements contain the same number of valence electrons. Similarly, you will find that the elements present in any one group have the same number of valence electrons. For example, elements fluorine (F) and chlorine (Cl), belong to group 17, Hence, we can say that groups in the Periodic Table signify an identical outershell electronic configuration. On the other hand, the number of shells increases as we go down the group.
All anomalies of Mendeleevs classification disappear.
ANOMALIES OF MODERN PERIODIC TABLE:-
- Explanation of the position of Isotopes (same atomic number put at one place in the same group)
- Cobalt with atomic number 27 came first and Nickel 28 should come later.
- Unlike atomic masses, atomic number is always a whole number, so there is no element between hydrogen and helium.
- Atomic number is denoted by ‘Z’ and equal to the number of protons in the nucleus of an atom.
- Elements with same number of valance electrons are placed in the same group
Li: 2, 1
Na: 2, 8, 1
K: 2, 8, 8, 1
- Outermost or valance shell in all the three contains 1 electron. These elements have been placed in the same group.
- Number of shells increases as we go down the group.
- Elements with same number of occupied shells are placed in the same period.
For example: Li(2, 1); Be(2, 2); B(2,3); C(2,4) these elements have the same number of shells.
- Each period marks a new electronic shell getting fitted.
- Maximum number of electrons that can be fitted in a shell is given by 2n2 where n is the shell number.
K Shell – 2 × (1)2 = 2, hence the first period has 2 elements.
L Shell – 2 × (2)2 = 8, hence the second period has 8 elements.
The third, fourth, fifth, sixth and seventh periods have 8, 18, 18, 32 and 32 elements respectively.
- The positions of the elements in the periodic table tells us its chemical reactivity.
- Valence electron determine the kind and number of bonds formed by the element.
TRENDS IN THE MODERN PERIODIC TABLE:-
VALENCY: As you know, the valency of an element is determined by the number of valence electrons present in the outermost shell of its atom.
- Valency of sulphur and magnesium is 2
- On moving from left to right from each period valency increases from 0 to 4 and then decreases to 0
- The valency remains the same moving down the groups.
The term atomic size refers to the radius of an atom. The atomic size may be visualised as the distance between the centre of the nucleus and the outermost shell of an isolated atom.
- Atomic size decreases as we move from left to right in a period because due to large positive charge on the nucleus the electrons are pulled more close to the nucleus which results in decreasing the size of the atom.
- Atomic size increases as we move down the group as new shells are being added and this increases the distance between the nucleus and the outermost electron.
METALLIC AND NON-METALLIC PROPERTIES:-
- Metallic character means the tendency of an atom to lose an electron.
- As the effective nuclear charge acting on the valence shell electrons increases across a period, the tendency to lose electrons will decrease as we move from left to right in a period.
- Metals are electropositive as they tend to lose electrons while forming bonds.
- Metallic character increases as we go down a group as the effective nuclear charge is decreasing.
- Non-metals, on the other hand, are electronegative. They tend to form bonds by gaining electrons.
- Non-metallic character increases across a period due to increase in effective nuclear charge that means tendency to gain electron increases
- Non-metallic character decreases down the group due to decrease in effective nuclear charge experienced by the valance electrons therefore the tendency to gain electrons decreases.
- In the middle of periodic table we have semi metals or metalloids because they exhibit the same properties as that of metals and non-metals
- oxides of metals are basic and that of non-metals are acidic in general.
- Periodicity of elements
- Cause of periodicity
Shaalaa.com | Periodic Classification of Elements part 7 (Trends in periods 1)
Taking into consideration the period of the elements given below, answer the following questions :
|Elements||Atomic Radius (pm)|
1) Arrange the above elements in a decreasing order of their atomic radii.
2) State the period to which the above elements belong.
3) Why this arrangement of elements period of modern periodic table ?
4) Which of the above elements have the biggest and the smallest atom?
5) What is the periodic trend observed in the variation of atomic radius while going from left to right within a period?
Atomic number of metal ‚A‛ is 11, while atomic number of metal ‚B‛ is 20. Which of them will be more reactive? Write the chemical reaction of dilute HCl with metal ‚A‛.
Fill in the blank:
The formulae of chloride of metal M is MCl2. The metal M belongs to ……………. group.
The atomic masses of three elements A, B and C having similar chemical properties are 7, 23 and 39, respectively.
- Calculate the average atomic mass of elements A and C.
- Compare the average atomic mass with atomic mass of B.
- What could the elements A, B and C be?