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Chemistry 9th Class Chemistry

Chemistry 9th – Important Definitions

Chemistry 9th              Important Definitions

   Chapter#1            Fundamentals Of Chemistry

 

 

  • Science: word science is derived from “scientia” means “knowledge”. The knowledge that provides understanding of this world and how it works is called science. The knowledge obtained through observations and experiments is called science.
  • Chemistry:The branch of science that deal with the composition, structure, properties and reactions of matter is called chemistry.
  • Physical chemistry:Physical Chemistry is defined as the branch of chemistry that deals with the relationship between the composition and physical properties of matter along with the changes in them.
  • Organic Chemistry: Organic Chemistry is the study of covalent compounds of carbon and hydrogen (hydrocarbons) and their derivatives.
  • Inorganic Chemistry: Inorganic chemistry deals with the study of all elements and their compounds except those of compounds of carbon and hydrogen (hydrocarbons) and their derivatives.
  • Industrial Chemistry: The branch of chemistry that deals with the manufacturing of chemical compounds on commercial scale, is called industrial chemistry.
  • Nuclear Chemistry :is the branch of chemistry that deals with the radioactivity, nuclear processes and properties.
  • Environmental Chemistry: It is the branch of chemistry in which we study about components of the environment and the effects of human activities on the environment.
  • Analytical chemistry: Analytical chemistry is the branch of chemistry that deals with separation and analysis of a sample to identify its components.
  • Matter: Anything that has mass and occupies space is called matter. Our bodies as well as all the things around us are examples of matter.
  • Substance:A piece of matter in pure form is termed as a substance. Every substance has a fixed composition and specific properties or characteristics. Examples: compounds, molecule, atom, element.
  • Mixture: Combination of two or more than two substances by physical means is called mixture. Example: sugar dissolved in water.
  • Physical properties: The properties those are associated with the physical state of the substance are called physical properties like colour, smell, taste, hardness, shape of crystal, solubility, melting or boiling points, etc. For example, when ice is heated, it melts to form water. When water is further heated, it boils to give steam. In this entire process only the physical states of water change whereas its chemical composition remains the same.
  • Chemical properties:The chemical properties depend upon the composition of the substance. When a substance undergoes a chemical change, its composition changes and a new substances are formed. For example, decomposition of water is a chemical change as it produces hydrogen and oxygen gases. All materials are either a substance or a mixture.
  • Elements: substances made up of same type of atoms, having same atomic number and cannot be decomposed into simple substances by ordinary chemical means are called elements.  Or substance in which all the atoms are identical and valenticle is called element. Example: Hydrogen.
  • Valency: The combining capacity of an element with other elements is called valency.
  • Homogenous Mixture:Mixtures that have uniform composition throughout are called homogeneous mixtures e.g. air, gasoline, ice cream.
  • Heterogenous Mixture :heterogeneous mixtures are those in which composition is not uniform throughout e.g. soil, rock and wood.
  • Compound:Compound is a substance made up of two or more elements chemically combined together in a fixed ratio by mass. Example: CO2.
  • Atom:(Derived from word atomos means indivisible but still atoms are divisible) smallest particle of an element which can take part in a chemical reaction is known as atom.  OR  The smallest building block of an element is called atom.

l Atomic number or proton number or identification number (Z):

The number of protons present in the nucleus of an atom is called proton number or atomic number. Example: Atomic number of Oxygen is 8.

  • Mass number:The mass number is the sum of number of protons and neutrons present in the nucleus of an atom. It is represented by symbol ‘A’. Example: Mass number of Oxygen is 16.
  • Relative Atomic Mass: The relative atomic mass of an element is the average mass of the atoms of that element as compared to 1/12th (one-twelfth) the mass of an atom of carbon- 12 isotope (an element having different mass number but same atomic number).
  • Atomic mass unit: One atomic mass unit is 1/12th the mass of one atom of carbon-12th.
  • Chemical formula: The symbolic representation of all the elements(atoms) in the compound is called chemical formula. OR The way of representing of a molecule or a compound using the symbols of its elements.
  • Empirical formula:The formula that shows simplest whole number ratio of elements present in a compound is called empirical formula. Example: Empirical formula of Benzene is CH.
  • Formula unit: The simplest whole number ratio of ions, as present in the ionic compound is called formula unit.   OR   The simplest unit taken as a representative of an ionic compound is called formula unit. Example: NaCl is the formula unit of sodium chloride.
  • Molecular Formula:formulae that show actual number of atoms of each element present in a molecule of that compound  is called molecular formula. Example: Molecular formula of Benzene is C6H6.
  • Molecular Mass : The sum of atomic masses of all the atoms present in one molecule of a molecular substance, is its molecular mass.
  • Formula mass; The sum of atomic masses of all the atoms present in one formula unit of a substance is called formula mass.
  • Chemical species: Atom or group of atoms which can take part in a chemical reaction or that is produced after a chemical reaction as a highly reactive substance is called chemical species.
  • Ion :Ion is an atom or group of atoms having a charge on it.
  • Cations :An atom or group of atoms having positive charge on it is called cation.   For example, Na+, K+ are cations.
  • Anion:An atom or a group of atoms that has a negative charge on it, is called anion. Examples: SO4-2, H2PO4, etc.
  • Atomic cation:An atom having positive charge on it is called atomic cation. Examples: Na+, Ca+, H+, etc.
  • Molecular cation(cationic molecular ion)A group of atoms or molecule having positive charge on it is called molecular cation. Examples: NH4+, H3O+, etc.
  • Atomic anion:An atom that has a negative charge on it, is called atomic anion. EXAMPLES: O-2, Cl, F, etc.
  • Molecular anion (anionic molecular ion):A group of atoms that has a negative charge on it, is called anion. Examples: SO4-2, H2PO4, etc.
  • Molecular ion:Group of atoms or molecule having a charge on it is called molecular ion. Examples: SO4-2, H2PO4 ,  NH4+, H3O+, etc.
  • Free Radicals:Free radicals are atoms or group of atoms possessing odd number of (unpaired) electrons.
  • Cleavage: The splitting or breakage of the bond between two atoms due to absorption of heat or light energy is called cleavage.
  • Homolytic cleavage:Equal breakage of bond between two atoms is called homolytic cleavage. As a result of homolytic cleavage free radicals are formed.
  • Example: H2+ energy → 2H
  • Heterolytic cleavage: unequal breakage of bond between two atoms is called heterolytic cleavage. Example: HCl + energy → H++ Cl
  • Molecule: The smallest component of a substance (an element or a compound) that can exist independently or freely in nature is called a molecule.
  • Polyatomic molecule:A molecule consisting of many atoms is called polyatomic molecule.For example: methane (CH4), sulphuric acid (H2SO4) and glucose (C6H12O6).
  • Homoatomic molecule:A Molecule containing same type of atoms, is called homoatomic molecule. For example: hydrogen (H2), ozone (O3), sulphur (S8) and phosphorus (P4).
  • Heteroatomic molecule:When a molecule consists of different kinds of atoms, it is called heteroatomic molecule. For example: CO2, H2O and NH3.
  • Gram Atomic Mass : The atomic mass of an element expressed in grams is called gram atomic mass or gram atom. It is also called a mole.
  • Gram Molecular Mass :The molecular mass of an element or a compound expressed in grams is called gram molecular mass or gram molecule. It is also called a mole.
  • Gram Formula Mass : The formula mass of an ionic compound expressed in grams is called gram formula mass or gram formula. This is also called a mole.. For example:
  • 1 gram formula of NaCI = 58.5 g = 1 mol of sodium chloride
  • 1 gram formula of CaCO3 = 100 g = 1 mol of calcium carbonate
  • Mole (Chemist secret unit) :A mole is defined as the amount(mass) of a substance that contains 6.02 x 1023 number of particles (atoms, molecules or formula units). OR mole is the atomic mass, molecular mass or formula mass of a substance expressed in grams is called mole.
  • Avogadro’s Number:Avogadro’s number is the number of particles ( atoms, ions or molecules) in one mole of a substance. OR 6.022 χ 1023 number of atoms, molecules or formula units (ions) is called avogadro’s number.

Chapter#2           STRUCTURE OF THE ATOM

 

  • Plum Pudding Model:According to this model Atoms were solid structures of positively charge with tiny negative particles stuck inside just like plums in the pudding.
  • Electrons: Negatively charged particles revolving in the orbits of an atom are called electrons.
  • Protons: Positive charged particles in the nucleus of an atom are called protons.

Neutrons: Neutral particles in the nucleus of an atom are called neutrons.

  • Electronic Configuration: The distribution or arrangment of electrons around the nucleus in various shells and sub shells according to their increasing energy is called electronic configuration.
  • Isotopes:The atoms of an element that have same atomic number but different mass number are known as isotopes. “OR” The atoms of an element that have same number of protons and electrons but different number of neutrons are called isotopes.
  • “OR”  Atoms of the same element having same chemical properties but different chemical properties are called isotopes.
  • Nuclear Fission: A nuclear reaction in which a heavy nucleus splits into smaller parts is called nuclear fission reaction. During this process energy is released which is used for different purposes.
  • Shells OR Orbits: The main energy levels  that electrons can occupy are called shells.  OR   The circular path around the nucleus of an atom in which electrons revolve are called shells. Exaples : K, L, M, N.
  • Sub-Shells :shells are further divided into sub energy levels called sub shells. Examples: s, p, d, f.

Chapter#3     Periodic Table and Periodicity of Properties

 

  • Periodic Table:-Periodic table is the arrangement of elements in order of increasing atomic number in such a way that those similar properties are placed one above other in the form of a table.

OR

Periodic table is the arrangement of elements in the form of a table in which elements with similar properties are placed in the same group.

  • Triads: A group of three elements in which the middle element has atomic mass average of the other two elements.
  • Mendeleev’s periodic law ;Properties of the elements are the periodic functions of their atomic masses.
  • Mosley’s Periodic Law OR Modern Periodic Law :Properties of the elements are the periodic functions of their atomic numbers.
  • Lanthanides ; the series that starts after Lanthanum is called Lanthanide series.
  • Actinides; The series that starts after Actinium is called actinide series.
  • Groups: Vertical columns in the periodic table are called groups.
  • Periods: The horizontal rows in the periodic table are called rows.
  • Block of periodic table : Based on the type of sub shells in which the last electrons are present periodic table is divided into blocks.
  • periodic properties ; periodic properties of elements are those properties of elements that undergoes gradual decrease or increase from left to right in a period or from top to bottom in a group in periodic table.
  • Atomic Radius ; The half of the distance between nuclei of two adjacent same atoms is called atomic radius.
  • OR Atomic radius is generally stated as being the total distance from an atom’s nucleus to the outermost orbital of electron.
  • Atomic Size:The distance between nuclei of two adjacent same atoms is called atomic size.
  • Shielding Effect: Shielding effect or screening effect is the decrease in effective nuclear charge force of attraction of nucleus) on an electron that is caused by the repulsive forces of other electrons between it and nucleus.
  • Ionization Energy;The amount of energy required to remove an electron from the valence shell of an isolated gaseous atom in its ground state is called ionization energy or ionization potential.
  • First Ionization Energy; the energy required to remove first electron from an isolated gaseous atom in its ground state is called first ionization energy.
  • Second Ionization Energy; the energy required to remove electron from an isolated mono-positive gaseous ion (M+) is called second ionization energy.
  • Electron Affinity; The amount of energy released when an electron is added to the valence shell of an isolated gaseous atom is called electron affinity.

Example; chlorine + 1e- → Cl    E.A= -349kj/mole.

  • Electronegativity:The ability of an atom to attract the shared pair of electrons toward itself is called electronegativity.

Chapter#4         Structure Of Molecules

 

  • Duplet rule: Attaining two electrons in the valence shell is called duplet rule. “OR “If electrons in the valence shell becomes two after bond formation the rule is called duplet rule. Example: This rule is applicable only for hydrogen and helium, both have only S sob-shell and can attain only two electrons.
  • Octet rule:Attaining eight electrons in the valence shell is called octet rule. OR If electrons in the valence shell become eight after bond formation, the rule is called octet rule. Example: Oxygen, Chlorine, etc.
  • Lone pair of electrons: The valence electrons pair that is not involved in bonding is called lone pair of electrons. Example: In NH3 molecule nitrogen contain one lone pair of electrons.
  • Bond pair of electrons:The valence electrons pair which are involved in bond formation are called bond pair of electrons. Example: NH3 molecule have three bond pair of electrons.
  • Chemical bond:A chemical bond is defined as a force of attraction between atoms that holds them together in a substance (molecule).
  • Ionic bond or Electrovalent bond:The type of chemical bond which is formed by complete transfer of electrons from one atom to other atom is called ionic bond. “OR” The electrostatic forces of attraction between positive (cation) and negative (anion) ion is called ionic bond.
  • Covalent Bond: The type of chemical bond which is formed by mutual sharing of electrons is called covalent bond.
  • Single covalent bond :   A covalent bond formed by the mutual sharing of one electron pair between two atoms is called a “Single   Covalent bond.” Examples: Bond in hydrogen molecule.
  • Double Covalent Bond : A covalent bond formed between two atoms by the mutual sharing of two electron pairs is called a “double   covalent bond”. It is denoted by double short line ().  Examples: The molecules like oxygen (O2) gas and ethene (C2H4) show such type of double covalent bonds.
  • Triple Covalent Bond:: Type of covalent bond in which each of the bonded atom contribute three electrons is called Triple Covalent bond.
  • Example : Bond in nitrogen molecule.
  • Polar covalent bond:A covalent bond formed between two different atoms is known as Polar covalent bond. OR  The type of covalent bond in which there is unequal sharing of electrons is called Polar covalent bond.
  • Non Polar Bond :A covalent bond formed between two like atoms is known as Non-polar bond. OR  Type of covalent bond that is formed due to equal sharing of electrons is called non polar covalent bond.
  • Coordinate covalent bond OR Dative bond: The type of chemical bond in which shared pair of electrons is donated(provided) by only one of the bonded  atoms is called coordinate covalent bond or dative bond.
  • Metallic Bond : The metallic bond is defined as a bond formed between metal atoms (positively charged ions) due to mobile or free electrons.
  • Intermolecular forces: Relatively weak type of attractive forces which are present in between the molecules are called intermolecular forces.
  • Dipole-Dipole interactions or vander walls forces:The net attractive forces between oppositely charged ends of two adjacent molecules are called dipole dipole interactions.
  • Hydrogen Bonding: The forces of attraction between hydrogen atom of one molecule and high electronegative atom in another molecule is called hydrogen bonding. OR The force of attraction between hydrogen atom of one molecule and nitrogen, oxygen and flourine of other molecule is called hydrogen bonding.

l Ionic Compounds :  The compounds which are formed due to ionic bonding are called ionic compounds.

l Covalent compounds: The compounds that are formed due to covalent bonding (sharing of electrons) are called Covalent compounds.

  • Polar Covalent compounds: Compounds that contain polar covalent bond are called polar compounds.
  • Non polar covalent compounds: that contain non polar covalent bond are called non polar compounds.
  • Coordinate Covalent Compounds: The compounds containing coordinate covalent bond are called coordinate covalent compounds.

  Chapter#5       PHYSICAL STATES OF MATTER

 

  • Matter:Any thing that has mass and occupy space is called matter. Matter exists in three physical states.
  • Gas or Gaseous state:State of matter that has neither fixed shape nor fixed volume is called gas. Examples: Oxygen, Hydrogen, etc.
  • Liquid state or liquid:the state of matter that has fixed volume but not fixed shape is called liquid.
  • Example: water, oil and milk.
  • Solid:State of matter that has fixed shape and fixed volume is called solid state.
  • Examples: pen, ice, salt, etc.
  • Diffusion:The  Spontaneous mixing up of molecules by random motion and collisions to form a homogeneous mixture.    ‘OR’
  • The spontaneous movement of molecules from a region of its higher concentration to a region of its lower concentration is called diffusion.
  • EFFUSION:The  escaping of gas molecules through a tiny hole into a space with lesser pressure is called effusion.
  • Pascal: The pressure equal one newton per square meter is called pascal.
  • Standard Atmospheric Pressure:It is the pressure exerted by the atmosphere at the sea level .  OR
  • It is defined as the pressure exerted by atmosphere at sea level.
  • Boyles Law: volume of a given mass of a gas is inversely proportional to its pressure provided the temperature remains constant.
  • “OR”
  • The product of pressure and volume of a fixed mass of a gas is constant at a constant temperature.
  • Absolute Temperature Scale or kelvin scale:A temperature scale that starts from 0k which is considered as absolute zero.
  • Absolute temperature: The temperature at which an ideal gas would have zero volume IS called absolute zero.
  • Or    the temperature on kelvin scale where zero is taken as absolute zero.
  • Charles Law:According to this law “ the volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant.   OR      When pressure is kept constant the volume of a given mass of a gas is directly proportional to absolute temperature on kelvin scale.
  • Evaporation : The process of changing of a liquid into a gas phase is called evaporation.
  • Vapour Pressure: The pressure exerted by the vapours of a liquid at equilibrium with the liquid at a particular temperature is called vapour pressure of a liquid.
  • Equilibrium state : The equilibrium is a state when rate of vapourization and rate of condensation is equal to each other but in opposite directions.
  • Boiling Point:Boiling point is the temperature at which vapor pressure of a liquid becomes equal to the atmospheric pressure or any external pressure. It is the temperature at which a liquid boils.
  • Freezing point:The temperature at which the  liquid and solid states of a substance coexist in dynamic equilibrium is called freezing point.
  • Density:Mass per unit volume is called density.
  • Melting point: The temperature at which the solid starts melting and coexists in dynamic equilibrium with liquid state is called melting point.
  • Amorphous Solids:Amorphous means shapeless. Solids in which the particles are not regularly arranged or their regular shapes are destroyed, are called amorphous solids. Example : plastic.
  • Crystalline Solids: Solids in which particles are arranged in a definite three-dimensional pattern are called crystalline solids. Examples of crystalline solids are diamond, sodium chloride, etc.
  • Allotropy: The existence of an element in more than one forms in same physical state is called allotropy.

 

Chapter#6                        Solution

 

  • Solution :A solution is a homogeneous mixture of two or more substances. example, the air we breathe is a solution of several gases.
  • Solute:The component of solution which is present in smaller quantity is called solute.
  • Solvent:The component of a solution which is present in larger quantity is called solvent.
  • Alloy:An Alloy is a homogenous mixture (Solid solution) of a metal with other metals or non metals.
  • Aqueous Solutions: The solution which is formed by dissolving a substance in water is called an aqueous solution.Example: Sugar dissolved in water.
  • Saturated solution: A solution containing maximum amount of solute at a given temperature is called saturated solution. “OR”  a Solution in which no more quantity of the solute can be dissolved at a specific temperature is called saturated solution. “OR”  On the particle level, a saturated solution is the one, in which undissolved solute is in equilibrium with dissolved solute. Example: 179 grams of sugar dissolved in 100 milliliters of water at 20 degrees Celsius.
  • Unsaturated Solution: A solution which contains lesser amount of solute than that which is required to saturate it at a given temperature, is called unsaturated solution. Example : 5 gram of sugar dissolved in 100 ml of water.
  • Supersaturated Solution:The solution that is more concentrated than a saturated solution is known as supersaturated solution. 400 Gram of sugar dissolved in 100 ml of water.
  • Dilute solution: Dilute solutions are those which contain relatively small amount of dissolved solute in the solution. Example: A solution containing 5 gram of sugar in 100 ml of water.
  • Concentrated solution:Concentrated solutions are those which contain relatively large amount of dissolved solute in the solution. For example, brine is a concentrated solution of common salt in water. 400 gram of sugar dissolved in 100 ml of water.
  • Concentration Units:There are various types of units used to express concentration of solution.
  • Percentage unit:Percentage unit of concentration refers to the percentage of solute present in a solution.
  • Percentage – mass/mass (%m/m): It is the number of grams of solute in 100 grams of solution. In this type of percentage composition both solute and solution are taken in grams (mass).
  • Example: 10% m/m sugar solution means that 10 g of sugar is dissolved in 90 g of water to make 100 g of solution.
  • Percentage – mass/volume (%m/v): It is the number of grams of solute dissolved in 100 cm3 (parts by volume) of the solution. In this type of percentage composition solute is taken in grams (mass) while solvent is taken in CM3 (volume).
  • Example: 10 % m/v sugar solution contains 10 g of sugar in 100 cm3 of the solution. The exact volume of solvent is not mentioned or it is not known.
  • Percentage – volume/mass (%v/m) :It is the volume in cm3 of a solute dissolved in 100 g of the solution. In this case solute is taken in CM3 (volume) while solution is taken in grams (mass).
  • Example:  10 % v/m alcohol solution in water means 10 cm of alcohol is dissolved in (unknown) volume of water so that the total mass of the solution is 100 g.
  • Percentage – volume /volume (% v/v): It is the volume in cm3 of a solute dissolved per 100 cm3of the solution. In this type of percentage composition both solute and solution are taken in CM3 or volume.
  • Example:30 percent alcohol solution means 30 cm3 of alcohol dissolved in sufficient amount of water, so that the total volume of the solution becomes 100 cm3.
  • Molarity:Number of moles of solute dissolved in one dm3 of the solution is called Molarity.
  • Solubility:The solubility of a solute in a solvent at a particular temperature is the number of grams of the solute necessary to saturate 100gm of the solvent at that temperature.
  • Colloid OR Colloidal solutions : Solutions in which the solute particles are larger than those present in the true solutions but not large enough to be seen by naked eye are called colloids or colloidal solutions.
  • Tyndall Effect: The effect of light scattering by the large particles when pass through a colloidal solution is called Tyndall effect.
  • Suspension:Suspensions are a heterogeneous mixture of undissolved particles in a given medium.

  Chapter#7                ELECTROCHEMISTRY

  • Electrochemistry:Electrochemistry is the branch of Chemistry that deals with the relationship between electricity and chemical reactions.
  • Oxidation: Addition of oxygen during a chemical reaction is called Oxidation.  “OR”  The removal of hydrogen during a chemical reaction is called oxidation.  “OR”  Loss of electrons by an atom or an ion is called Oxidation.
  • Reduction:The removal of oxygen during a chemical reaction is called reduction.   “OR”  The addition of hydrogen during a chemical reaction is called Reduction.  “OR”  The addition of electron by an atom or ion is called reduction.
  • Oxidation State OR Oxidation Number :Oxidation state or oxidation number (O.N.) is the apparent charge assigned to an atom of an element in a molecule or in an ion. For example: in HCl, oxidation number of H is +1 and that of CI is -1.
  • Oxidizing Agents: An Oxidizing agent is the specie that oxidise a substance by taking electrons from it is called Oxidizing agent. The substance (atom or ion) which is reduced itself by gaining electrons is also called oxidizing agent.
  • Reducing agent: Reducing agent is the specie that reduces a substance by donating electron to it. The substance (atom or ion) which is oxidized by losing electrons is also called reducing agent .
  • Oxidation:The reaction in which oxidation number of an atom or ion increases is called oxidation reaction.
  • Reduction:The reaction in which oxidation number of an atom or ion decreases is called reduction reaction.
  • Electrolytes : The substances, which can conduct electricity in their aqueous solutions or molten states, are called electrolytes. For example, solutions of salts, acids or bases are good electrolytes.
  • Strong Electrolytes:The electrolytes which ionize almost completely in their aqueous solutions and produce more ions, are called strong electrolytes. Example of strong electrolytes are aqueous solutions of NaCl, NaOH and H2SO4, etc.
  • Weak Electrolytes : The electrolytes which ionize to a small extent when dissolved in water and could not produce more ions are called weak electrolytes. Acetic acid (CH3COOH) and Ca(OH)2when dissolved in water, ionize to a small extent and are good examples of weak electrolytes.
  • Non-Electrolytes :The substances, which do not ionize in their aqueous solutions and do not allow the current to pass through their solutions, are called non-electrolytes. For example, sugar solution and benzene are non-electrolytes.
  • ELECTROCHEMICAL CELLS:Electrochemical cell is a system in which two electrodes are dipped in the solution of an electrolyte which are connected to the battery.
  • Electrolytic cells:The type of electrochemical cell in which a non-spontaneous (energy is used) chemical reaction takes place when electric current is passed through the solution, is called an electrolytic cell.
  • Electrolysis: The chemical decomposition of a compound into its components by passing current through the solution of the compound or in the molten state of the compound.
  • Galvanic Cell: The electrochemical cell in which a spontaneous chemical reaction takes place and generates electric current is called galvanic or voltaic cell. Example of this type of cell is a Daniel cell.
  • Electrochemical Industries: The industries in which various chemicals are produced by the use of electrolytic cell or electric current are called electrochemical industries.
  • Corrosion:Corrosion is slow and continuous eating away of a metal by the surrounding medium.
  • Rusting of Iron : The corrosion of iron is called rusting.
  • Metallic Coating: Thin films of material bonded to metals in order to protect the metal from corrosion and to give it attractive appearance is called Metallic Coating.
  • Zinc coating or Galvanizing :The process of coating a thin layer of zinc on iron is called galvanizing.
  • Electrolytic method (Electroplating) : Electroplating is depositing of one metal over the other by means of electrolysis.

  Chapter#8              CHEMICAL REACTIVITY

l METALS : Metals are the elements (except hydrogen) which are electropositive and form cations by losing electrons.

  • Transition metals: The elements in which d-orbital are in the process of filling, constitute a group of metals called transition metals or d-group elements.
  • Noble Metals:A metal that resist chemical action, does not corrode and is not easily attacked by acids is called noble metal.
  • Non metals :Non-metals are elements that form negative ions (anions) by gaining electrons.
  • Malleable: A metal that can be hammered into sheets is called malleable.
  • Ductile:The metals that can be drawn into wires is called ductile.
  • Electropositivity:The ability of atoms to lose electrons easily is called metallic character or electropositivity.

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