Fundamental Chemistry for UPSC Prelims
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- Chemistry is often referred to as the central science because it connects and bridges various scientific disciplines. It delves into the composition, structure, properties, and changes of matter, providing a profound understanding of the world around us. This article aims to explore some fundamental concepts in chemistry, touching upon states of matter, chemical changes, atomic models, and separation techniques.
Fundamental Chemistry for UPSC Prelims – (PPT Lec 4)
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“Journey Through the Wonders of Chemistry: From the 7 States of Matter to Acids, Bases, and Salts”
Chemistry is the fascinating study of matter, its properties, and the changes it undergoes. From the seven states of matter to the intricacies of chemical bonding, this article takes you on a captivating journey through the diverse realms of chemistry.
The 7 States of Matter
Here’s a table summarizing the 7 states of matter along with examples:
| State of Matter | Description | Example |
|---|---|---|
| 1. Solid | – Definite shape and volume | – Ice, Wood, Metal |
| 2. Liquid | – Definite volume, takes the shape of its container | – Water, Oil, Mercury |
| 3. Gas | – No definite shape or volume, fills the container | – Air, Oxygen, Hydrogen |
| 4. Plasma | – High energy, ionized gas with free electrons | – Stars, Lightning, Neon Lights |
| 5. Bose-Einstein Condensate | – Extremely low temperatures, particles in the same quantum state | – Ultra-cold atoms near absolute zero |
| 6. Fermionic Condensate | – Ultra-cold temperatures, fermions in a collective quantum state | – Supercooled fermionic particles |
| 7. Quark-Gluon Plasma | – Extreme heat and energy, quarks and gluons no longer confined | – Early universe moments, High-energy collisions |
This table provides a concise overview of the 7 states of matter, from the familiar solid, liquid, and gas to the exotic states like plasma, Bose-Einstein condensate, fermionic condensate, and quark-gluon plasma, along with examples illustrating each state.
Physical and Chemical Changes
Here’s a table summarizing physical and chemical changes along with examples:
| Type of Change | Description | Example |
|---|---|---|
| Physical Change | – Alteration in the physical properties without changing the substance’s composition | – Ice melting into water, Cutting paper |
| Chemical Change | – Formation of new substances with different properties | – Rusting of iron, Burning wood |
| Melting and Freezing | – Physical change involving the transition between solid and liquid states | – Ice (solid) melting into water (liquid) |
| Sublimation | – Transition from a solid directly to a gas without passing through the liquid phase | – Dry ice (solid CO2) sublimating into CO2 gas |
| Vaporization | – Physical change from a liquid to a gas | – Boiling water into steam, Evaporating alcohol |
| Evaporation/Vaporization | – Conversion of a liquid to a vapor, typically at the liquid’s surface | – Puddles drying up, Wet clothes drying |
| Condensation and Deposition | – Transition from a gas to a liquid or solid | – Water vapor condensing into clouds, Frost forming on a windowpane |
| Element, Mixture, and Compound | – Classification of substances based on their composition | – Oxygen (element), Saltwater (mixture), Water (compound) |
| A mixture of Two Solids | – Combination of two different solid substances | – Salt and sand mixture |
| A mixture of Solid and Liquid | – Combination of a solid and a liquid substance | – Sugar dissolved in water (solution) |
| By Filtration | – Separates solid particles from a liquid by passing the mixture through a porous material (filter) | Separation of sand from water using filter paper |
| By Crystallization | – Formation of pure solid crystals from a solution by cooling or evaporating the solvent | – Obtaining salt crystals from a saltwater solution
Making rock candy from a sugar solution |
| By Centrifugation | – Uses centrifugal force to separate components based on their density differences | – Separation of cream from milk in a centrifuge |
| By Chromatography | – Separates components of a mixture based on their differential affinity for a stationary phase and a mobile phase | – Separation of ink pigments on paper in paper chromatography |
| By Evaporation | – Vaporization of the liquid component, leaving behind the solid components | – Saltwater evaporating to obtain salt crystals |
| By Distillation | – Separation based on differences in boiling points; the liquid is vaporized and condensed to form a pure liquid | – Distilling alcohol from a fermented liquid
Separation of alcohol from a water-alcohol mixture |
| Sedimentation and Decantation | – Separation method based on differences in density, allowing particles to settle | – Allowing sand to settle in water, then pouring off the clear water |
This table provides a comprehensive overview of physical and chemical changes, as well as various methods of separation with examples illustrating each concept.
Why Does Food Take Time to Cook at High Altitudes?
Here’s a table summarizing why food takes time to cook at high altitudes along with examples:
| Factor | Description | Example |
|---|---|---|
| Reduced Atmospheric Pressure | – Lower air pressure at higher altitudes affects the boiling points of liquids | – Water boils at a lower temperature, affecting cooking times |
| Boiling Point Elevation | – Higher altitudes increase the time it takes for water to reach its boiling point | – Boiling pasta takes longer at high altitudes compared to sea level |
| Temperature Fluctuations | – Rapid temperature changes due to lower boiling points may impact cooking consistency | – Difficulty in achieving precise temperatures for certain recipes |
| Decreased Humidity | – Low humidity at high altitudes can lead to faster evaporation, drying out food | – Baked goods may need adjustments to prevent them from drying out |
| Leavening Agents’ Behavior | – Leavening agents like yeast and baking powder may act differently at higher altitudes | – Bread may rise more quickly or unevenly, affecting the final texture |
| Effects on Cooking Methods | – Grilling and roasting may require adjustments due to faster moisture loss | – Grilled meats may need shorter cooking times to prevent drying out |
| Examples of Adjustments | – Longer cooking times for boiling and simmering | – Adjustments to recipes for baking, including changes in flour and leavening agent amounts |
| Pressure Cooker Benefits | – Pressure cookers can mitigate the effects of reduced pressure, reducing cooking times | – Faster cooking of beans and tougher meats in a pressure cooker |
This table provides insights into the factors influencing cooking times at high altitudes, the challenges they pose, and examples of adjustments and tools that can be employed to overcome these challenges.
Cooking at high altitudes alters the boiling point due to reduced atmospheric pressure, impacting the time required for food to reach the desired state.
Evaporation/Vaporization
Natural processes like drying clothes involve the conversion of liquids to vapors through evaporation.
Condensation and Deposition
Opposite to vaporization, condensation turns vapors into liquids. Deposition sees gases becoming solids without passing through a liquid phase.
Elements, Mixtures, and Compounds
Here’s a table summarizing elements, mixtures, and compounds along with examples:
| Type of Substance | Description | Example |
|---|---|---|
| Element | – Fundamental substance that cannot be broken down into simpler substances by chemical means | – Oxygen (O2), Gold (Au), Hydrogen (H2) |
| Mixture | – Combination of two or more substances in which each substance retains its individual properties | – Salad (lettuce, tomatoes, and dressing), Air (mix of gases) |
| A mixture of Two Solids | – Combination of two different solid substances | – Sand and salt mixture, Iron and sulfur mixture |
| Sublimation in Mixtures | – Some mixtures involve substances undergoing sublimation, where solid components transform directly into gas | – Iodine and sand mixture (sublimation of iodine) |
| A mixture of Solid and Liquid | – Combination of a solid and a liquid substance | – Salt dissolved in water, Sand in water (Suspension) |
| By Filtration | – Separation method based on particle size differences | – Filtering sand from water, Removing tea leaves from liquid |
| By Crystallization | – Separation method based on differences in solubility and crystallization | – Obtaining salt crystals from a saltwater solution |
| By Centrifugation | – Separation method based on differences in density and particle size | – Separating suspended particles in blood |
| By Chromatography | – Separation method based on differences in solubility and mobility | – Separating pigments in ink or plant leaves |
| By Evaporation | – Separation method based on the vaporization of a solvent | – Recovering salt from saltwater by evaporating the water |
| By Distillation | – Separation method based on differences in boiling points | – Distilling alcohol from a fermented liquid |
| Compound | – Substance composed of two or more elements chemically combined in fixed ratios | – Water (H2O), Carbon dioxide (CO2), Sodium chloride (NaCl) |
| Formation of Compounds | – Elements chemically react to form compounds with unique properties | – Hydrogen (H2) reacts with Oxygen (O2) to form Water (H2O) |
| Importance of Compounds | – Compounds exhibit distinct properties different from their constituent elements | – Sodium chloride (NaCl) tastes salty, Sodium (Na) and Chlorine (Cl) are both reactive elements, but their compound is stable |
This table provides a comprehensive overview of elements, mixtures, and compounds, along with various methods of separation and examples illustrating each concept.
Atom and Mole Concept
Here’s a table summarizing the Atom and Mole Concepts along with examples:
| Concept | Description | Example |
|---|---|---|
| Atom | – The basic unit of matter, consisting of a nucleus composed of protons and neutrons, with electrons orbiting around the nucleus | – Hydrogen atom (1 proton, 1 electron), Carbon atom (6 protons, 6 neutrons, 6 electrons) |
| Mole Concept | – A unit used in chemistry to express amounts of a substance, representing Avogadro’s number of entities (atoms, molecules, ions) | – 1 mole of water molecules contains approximately 6.022 x 10^23 molecules |
| Atomic Mass | – The mass of an atom, typically measured in atomic mass units (amu) | – The atomic mass of carbon is approximately 12 amu |
| Constituents of an Atom | – Atoms consist of protons, neutrons, and electrons | – The helium atom has 2 protons, 2 neutrons, and 2 electrons |
| Isotopes | – Atoms of the same element with different numbers of neutrons | – Carbon-12 and Carbon-14 are isotopes of carbon |
| Isobars | – Atoms with the same mass number but different atomic numbers | – Oxygen-16 and Fluorine-16 are isobars |
| Thomson’s Atomic Model | – Proposed by J.J. Thomson, the “plum pudding” model suggesting electrons are embedded in a positive sphere | – Electrons dispersed in a positive “pudding” of protons for balance |
| Rutherford’s Model of an Atom | – Proposed by Ernest Rutherford, introducing the concept of a dense, positively charged nucleus | – Electrons orbiting around a small, positively charged nucleus |
| Bohr’s Model of an Atom | – Proposed by Niels Bohr, electrons orbit the nucleus in quantized energy levels | – Electrons in specific orbits, each corresponding to a certain energy level |
| Plank’s Quantum Theory | – Introduced by Max Planck, quantizes energy levels, laying the foundation for quantum mechanics | – Energy of electrons in atoms is quantized, leading to discrete energy levels |
| Periodic Classification of Elements | – Arrangement of elements based on their atomic number and similar properties | – Elements in the same group (column) share similar chemical properties |
| Mendeleev’s Periodic Table | – An early periodic table arranged elements based on atomic mass, predicting missing elements | – Predicted the existence and properties of gallium, germanium, and scandium |
| Modern Periodic Law | – Elements are arranged in order of increasing atomic number, revealing periodic patterns | – Periodic repetition of properties such as valence electrons and atomic radius |
| Trends in the Modern Periodic Table | – Observable patterns in properties as one moves across or down the periodic table | – Electronegativity increases from left to right across a period |
This table provides an overview of the Atom and Mole Concept, highlighting key concepts, definitions, and examples associated with these fundamental principles in chemistry.
Periodic Classification of Elements
Here’s a table summarizing the Periodic Classification of Elements along with examples:
| Aspect | Description | Example |
|---|---|---|
| Periodic Classification of Elements | – Arrangement of elements based on their atomic number and similar properties | – Elements in the same group (column) share similar chemical properties |
| Mendeleev’s Periodic Table | – An early attempt to organize elements based on atomic mass, leaving gaps for predicted elements | – Predicted the existence and properties of gallium, germanium, and scandium |
| Modern Periodic Law | – Elements are arranged in order of increasing atomic number, revealing periodic patterns | – Periodic repetition of properties such as valence electrons and atomic radius |
| Periods and Groups | – Periods are horizontal rows, groups (families) are vertical columns | – Period 3 contains elements like sodium and chlorine, Group 18 (Noble Gases) |
| Trends in the Modern Periodic Table | – Observable patterns in properties as one moves across or down the periodic table | – Electronegativity increases from left to right across a period |
| Major Periodic Trends | – Key characteristics that change predictably across periods and down groups | – Electronegativity, Ionization Energy, Atomic Radius, Metallic Character |
| Electronegativity | – Tendency of an atom to attract electrons towards itself in a chemical bond | – Fluorine is highly electronegative, while Francium is the least electronegative |
| Ionization Energy | – Energy required to remove an electron from an atom or a positive ion | – Helium has a high ionization energy due to its stable electron configuration |
| Atomic Radius | – The size of an atom, typically defined as the distance from the nucleus to the outermost electron | – Atomic radius increases down a group, decreases across a period |
| Melting Point | – Temperature at which a substance changes from a solid to a liquid | – Generally, metals have higher melting points than nonmetals |
| Metallic Character | – Degree to which an element exhibits metallic properties | – Sodium is a metal with high metallic character, while fluorine is a nonmetal |
| Periodic Table | – Visual representation of the periodic classification of elements | – The modern periodic table organizes elements based on atomic number |
This table provides an overview of the Periodic Classification of Elements, highlighting key concepts, principles, and examples associated with the organization of elements in the periodic table.
Chemical Bonding
Here’s a table summarizing Chemical Bonding along with examples:
| Type of Chemical Bond | Description | Example |
|---|---|---|
| Ionic Bonding | – Formed by the transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other | – Sodium (Na) transferring an electron to Chlorine (Cl), forming Na+ and Cl- ions |
| Conditions and Properties of Ionic Bond | – Ionic bonds typically form between metals and nonmetals with a significant difference in electronegativity | – NaCl (Table salt), MgO (Magnesium oxide) |
| Covalent Bonding | – Formed by the sharing of electrons between atoms, resulting in the formation of molecules | – Hydrogen (H2), Oxygen (O2), Methane (CH4) |
| Types of Covalent Bond | – Single, double, or triple bonds formed by the sharing of one, two, or three pairs of electrons, respectively | – Single bond in H2 (H-H), Double bond in O2 (O=O), Triple bond in N2 (N≡N) |
| Coordinate Bonding | – Special type of covalent bond where both shared electrons come from one atom | – Formation of ammonia (NH3) involves a coordinate bond between nitrogen and hydrogen |
| Characteristics of Coordinate Covalent Bond | – The atom donating both electrons is called the donor atom, while the other is the acceptor atom | – Ammonium ion (NH4+) formation through a coordinate bond between nitrogen and hydrogen |
| Hydrogen Bond | – Attraction between a hydrogen atom covalently bonded to a highly electronegative atom and another electronegative atom | – Water molecules (H2O) interacting through hydrogen bonding |
| Bond Energy (Bond Enthalpy) | – Energy required to break a chemical bond or the energy released when a bond is formed | – The bond energy of the O-H bond in water is approximately 464 kJ/mol |
| Ionic, Covalent, and Metallic Character | – Describes the nature of bonding within substances, ranging from nonmetals (covalent) to metals (metallic) | – Sodium (Na) exhibits a metallic character, while chlorine (Cl) exhibits a covalent character |
| Ionic vs. Covalent Bonds | – Differences in electron transfer, bond formation, and properties between ionic and covalent bonds | – NaCl (ionic) vs. H2O (covalent) |
| Polarity in Covalent Bonds | – Results from an unequal sharing of electrons, leading to a separation of charges | – Water (H2O) has a polar covalent bond due to the difference in electronegativity between hydrogen and oxygen |
| Intermolecular Forces | – Forces between molecules that influence physical properties such as boiling and melting points | – London Dispersion Forces, Dipole-Dipole Interactions, and Hydrogen Bonding |
| Formation of Polyatomic Ions | – Group of atoms with an overall charge, formed through the loss or gain of electrons | – Formation of sulfate ion (SO4^2-) involves the sharing of electrons among sulfur and oxygen atoms |
This table provides an overview of various aspects of chemical bonding, including different types of bonds, their characteristics, and examples illustrating each concept.
Acids, Bases & Salts
Here’s a table summarizing Acids, Bases, and Salts along with examples:
| Type of Substance | Description | Example |
|---|---|---|
| Acids | – Substances that release hydrogen ions (H+) when dissolved in water, have a sour taste, and turn blue litmus paper red | – Hydrochloric acid (HCl), Citric acid (found in citrus fruits), Acetic acid (vinegar) |
| Strong Acids | – Completely dissociate into ions in water, producing a large number of hydrogen ions | – Hydrochloric acid (HCl), Sulfuric acid (H2SO4) |
| Weak Acids | – Partially dissociate into ions in water, producing a smaller number of hydrogen ions | – Acetic acid (CH3COOH), Carbonic acid (H2CO3) |
| Bases | – Substances that release hydroxide ions (OH-) when dissolved in water, have a bitter taste, and turn red litmus paper blue | – Sodium hydroxide (NaOH), Calcium hydroxide (Ca(OH)2), Ammonia (NH3) |
| Strong Bases | – Completely dissociate into ions in water, producing a large number of hydroxide ions | – Sodium hydroxide (NaOH), Potassium hydroxide (KOH) |
| Weak Bases | – Partially dissociate into ions in water, producing a smaller number of hydroxide ions | – Ammonia (NH3), Aluminum hydroxide (Al(OH)3) |
| Acids and Bases in Everyday Life | – Examples of acids and bases commonly encountered in daily activities | – Lemon juice (acidic), Soap (basic), Baking soda (basic) |
| Properties of Acids | – Sour taste, turn blue litmus paper red, react with metals to produce hydrogen gas, and conduct electricity when dissolved in water | – Hydrochloric acid (HCl) reacts with zinc to produce zinc chloride and hydrogen gas |
| Properties of Bases | – Bitter taste, turn red litmus paper blue, feel slippery (soapy), and conduct electricity when dissolved in water | – Sodium hydroxide (NaOH) reacts with aluminum to produce sodium aluminate and hydrogen gas |
| Neutralization Reaction | – Reaction between an acid and a base to form water and a salt | – Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to produce water (H2O) and sodium chloride (NaCl) |
| Salts | – Ionic compounds formed by the neutralization of an acid and a base | – Sodium chloride (NaCl), Calcium sulfate (CaSO4), Potassium nitrate (KNO3) |
| Formation of Salts | – Salts are formed when the hydrogen ions from an acid are replaced by metal ions or ammonium ions | – Reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) produces sodium chloride (NaCl) and water (H2O) |
This table provides an overview of acids, bases, and salts, including their definitions, properties, examples, and reactions.
Tooth Decay and pH of Soil
Acidic conditions contribute to tooth decay, while soil pH impacts plant growth and nutrient availability.
Salts and Water of Crystallization
Understanding salts and their formation, including the presence of water of crystallization, adds depth to our comprehension of chemical compounds.
Also read: Test Book PDF
(Potential of Hydrogen) pH value Table
Here’s a table summarizing pH values along with examples:
| pH Value | Acidity/Alkalinity Level | Example |
|---|---|---|
| 0-2 | Strong Acidic | – Hydrochloric acid (HCl) |
| 3 | Moderately Acidic | – Lemon juice |
| 4 | Weakly Acidic | – Tomato juice, Vinegar |
| 5 | Slightly Acidic | – Black coffee, Rainwater |
| 6-7 | Neutral | – Pure water, Milk |
| 8 | Slightly Alkaline | – Sea water, Baking soda |
| 9 | Weakly Alkaline | – Toothpaste, Soap |
| 10 | Moderately Alkaline | – Milk of Magnesia |
| 11-14 | Strong Alkaline | – Ammonia solution, Bleach |
This table provides an overview of pH values, their corresponding acidity or alkalinity levels, and examples of substances at different pH levels. The pH scale ranges from 0 to 14, with 7 being neutral, values below 7 indicating acidity, and values above 7 indicating alkalinity.
Table of Covalent bond
Here’s a table summarizing Covalent Bonds along with examples:
| Concept | Description | Example |
|---|---|---|
| Covalent Bond | – A type of chemical bond formed by the sharing of electrons between two nonmetal atoms | – Hydrogen molecule (H2), Oxygen molecule (O2) |
| Single Covalent Bond | – Sharing of one pair of electrons between two atoms | – H2 (Hydrogen gas), Cl2 (Chlorine gas) |
| Double Covalent Bond | – Sharing of two pairs of electrons between two atoms | – O2 (Oxygen gas), CO2 (Carbon dioxide) |
| Triple Covalent Bond | – Sharing of three pairs of electrons between two atoms | – N2 (Nitrogen gas), C2H2 (Acetylene) |
| Polar Covalent Bond | – Unequal sharing of electrons, resulting in a partial positive and partial negative charge | – HCl (Hydrochloric acid), H2O (Water) |
| Nonpolar Covalent Bond | – Equal sharing of electrons, resulting in no significant charge separation | – Cl2 (Chlorine gas), N2 (Nitrogen gas) |
| Coordinate Bond (Dative Bond) | – A special type of covalent bond where both shared electrons come from one atom | – Formation of ammonia (NH3) involves a coordinate bond between nitrogen and hydrogen |
| Characteristics of Covalent Bonds | – Formed between nonmetal atoms, involve sharing of electrons, can exist as molecules | – Methane (CH4), Ethanol (C2H5OH) |
| Molecular Structure | – Arrangement of atoms in a molecule, influenced by the number and type of bonds | – Water (H2O) has a bent molecular structure, methane (CH4) has a tetrahedral structure |
| Bond Length | – The average distance between the nuclei of two bonded atoms | – The bond length in a carbon-carbon single bond (C-C) is approximately 154 picometers |
| Bond Angle | – The angle between two adjacent bonds in a molecule | – Water (H2O) has a bond angle of approximately 104.5 degrees |
| Hybridization | – The mixing of atomic orbitals to form new, hybrid orbitals | – Sp3 hybridization in methane (CH4), sp2 hybridization in ethene (C2H4) |
| Resonance | – The phenomenon where multiple Lewis structures can represent a molecule | – Ozone (O3) exhibits resonance structures |
| Examples of Covalent Compounds | – A variety of molecules formed by covalent bonds | – Methane (CH4), Carbon dioxide (CO2), Ethanol (C2H5OH) |
This table provides an overview of covalent bonds, including their types, characteristics, and examples of molecules formed by covalent bonding.
Thomson’s Atomic Model, Rutherford’s Model of an Atom, Bohr’s Model of an Atom, and Planck’s Quantum Theory
Here’s a table summarizing Thomson’s Atomic Model, Rutherford’s Model of an Atom, Bohr’s Model of an Atom, and Planck’s Quantum Theory:
| Atomic Model | Description | Example |
|---|---|---|
| Thomson’s Atomic Model | – Proposed by J.J. Thomson, also known as the “plum pudding” model | – Suggested that atoms were a positively charged “pudding” with negatively charged electrons dispersed in it |
| Rutherford Model of an Atom | – Proposed by Ernest Rutherford after the gold foil experiment | – Introduced the concept of a small, dense, positively charged nucleus at the center of an atom, with electrons orbiting around it |
| Bohr’s Model of an Atom | – Proposed by Niels Bohr, based on the quantization of electron energy levels | – Electrons orbit the nucleus in specific, quantized energy levels, jumping between them when gaining or losing energy |
| Planck’s Quantum Theory | – Developed by Max Planck to explain the quantization of energy levels | – Introduces the idea that energy is emitted or absorbed in discrete units called quanta |
| Key Features and Contributions | – Discovered the electron and its negatively charged nature | – Disproved the idea of the atom as a continuous, uniform pudding |
| – Established the existence of a small, dense nucleus in the atom | – Addressed the problem of electrons spiraling into the nucleus by proposing quantized energy levels | |
| – Provided a model for the stability of the atom with electrons in fixed orbits | – Contributed to the understanding of the behavior of electrons in atoms, specifically their energy levels | |
| – Influenced the development of subsequent atomic models | – Laid the groundwork for the modern understanding of atomic structure | |
| Limitations/Drawbacks | – Unable to explain the stability of the atom with orbiting electrons | – Did not fully account for the observed spectra of atoms |
| – Could not explain the discrete spectral lines observed in hydrogen | – Failed to predict the exact position of electrons in orbits | |
| – Did not incorporate the wave-particle duality of electrons | – Limited applicability to single-electron systems | |
| Significance in Atomic Theory | – Paved the way for the development of more sophisticated atomic models | – Contributed to the understanding of electron behavior and quantization of energy levels |
| – Highlighted the existence of subatomic particles within the atom | – Played a crucial role in explaining the stability of atoms through quantized energy levels |
This table provides an overview of Thomson’s Atomic Model, Rutherford Model of an Atom, Bohr’s Model of an Atom, and Planck’s Quantum Theory, including their key features, examples, limitations, and significance in atomic theory.
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