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CHEMISTRY KEY POINTS

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Published in: Chemistry
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ATOMS AND MOLECULES, CLASS IX

Arun M / Faridabad

4 years of teaching experience

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Teaches: Mathematics, IIT JEE Mains

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  1. Class : IX CHEMISTRY KEY POINTS Sub •ect : Chemistr Board : CBSE TOPIC : ATOMS & MOLECULES Law of conservation of Mass : The total mass of the products of a chemical reaction is equal to the total mass of the reactants that have combined OR The mass can neither be created nor destroyed in a chemical reaction. Law of constant proportions : A pure chemical compound always consists of the same elements that are combined together in a fixed ( or definite ) proportion by mass. Atomic Mass Unit (u ): An atomic mass unit may be defined as the mass of one twelfth ( 1 / 12 ) of the mass of one atom of carbon taken as 12. Gram Atomic Mass : The atomic mass of an element expressed in grams which is numerically equal to the mass in u. Molecules : Molecule represents a group of two or more atoms ( same or different ) chemically bonded to each other and held tightly by strong attractive forces OR A molecule can be defined as the smallest particle of an element or a compound that is capable of an independent existence and shows all the properties of that substance. Atomicity . The number of the atoms constituting a molecule of an element represent its Atomicity.
  2. IONS : An atom or group of atoms having positive or negative charges is called Ion. Chemical Formulae : Chemical formula may be defined as the short hand representation of the name of a molecule in terms of the symbols of the constituting atoms. Valency : Valency is defined as the combining capacity of an atom with atoms of other element Mole Concept : a) A mole denotes Avogadro's number ( No or NA = 6.022 x 1023) of particles ( atoms, molecules or ions ). b) The mass of 1 mole of a substance is equal to its relative atomic mass OR molecular mass in gms. c) The atomic mass of an element gives us the mass of ONE atom of that element in atomic mass unit (u). d) Mass of one mole of atom of that element ( Molar Mass ) we have to change the unit of atomic mass from u to g. Examples - a) b) c) d) a) b) c) d) a) b) c) d) Atomic mass of hydrogen = 1 u So gram atomic mass of hydrogen = 1 g 1 u hydrogen has only ONE atom of hydrogen Whereas 1 g hydrogen has 1 mole atoms (6.022 x 1023 atoms of hydrogen ) Atomic mass of oxygen = 16 u So gram atomic mass of oxygen = 16 g 16 u oxygen has only ONE atom of oxygen Whereas 16 g oxygen has 1 mole atoms (6.022 x 1023 atoms of oxygen ) Molecular mass of water = 18 u So gram molecular mass of water = 18 g 18 u water has only ONE molecule of water Whereas 18 g water has 1 mole molecules (6.022 x 1023 molecules of water )
  3. NAME AND SYMBOLS OF SOME COMPOUNDS NAME Aluminium oxide Ammonium sulphate Aluminium chloride Ammonia Ammonium carbonate Aluminium borate Aluminium hydroxide Ammonium chloride Acetic acid Aluminium sulphate Baking powder / Baking soda Barium oxide Carbon tetrachloride Calcium oxide Calcium hydroxide Copper nitrate Carbon dioxide Copper(ll) sulphate Calcium phosphate Carbon monoxide Castic soda Common salt Calcium chloride Calcium carbonate Calcium oxide Carbon disulphide Chloroform Calcium nitrate Dinitrogen monoxide Dinitrogen trioxide Dinitrogen tetraoxide Dinitrogen pentoxide Ethyne Ethyl alcohol Ethane Ethylene Glucose Hydrochloric acid Hydrogen sulphide SYMBOL A1203 (NH4)2S04 AIC13 NH3 (NH4)2C03 or AlB03 NH4Cl CH3COOH NaHC03 Ba202 or Bao CCU Ca202 or CaO CuN03 C02 co NaOH NaCl CaC12 CaC03 CaO CS2 CHC13 N20 N203 N204 N205 C2H2 C2H50H C2H6 C2H4 C6H1206 I-ICI OTHER NAME Ethanoic acid Sodium bicarbonate Tetrachloromethane Sodium hydroxide Sodium chloride Quick lime Ethanol Ethene Hydrogen chloride
  4. Hydrogen bromide Magnesium chloride Methane Methanol Magnesium sulphate Magnesium hydroxide Methyl alcohol Magnesium carbonate Magnesium oxide Nitric acid Nitrogen monoxide Nitrogen dioxide Potassium sulphate Potassium bromide Potassium dichromate Potassium chromate Phosphoric acid Potassium carbonate Potassium nitrate Potassium chloride Phosphorous trichloride Phosphorous pentachloride Sodium nitrate Sodium carbonate Sulphuric acid Sodium phosphate Sulphur dioxide Sulphur trioxide Sucrose Sodium sulphate Sodium oxide Sodium sulphide Water Zinc oxide Zinc sulphate HBr MgC12 CH4 CH30H MgS04 CH30H or MgC03 Mgo HN03 NO N02 K2S04 KBr 1
  5. NAME AND SYMBOLS OF SOME IONS NAME Ammonium Bromide Chloride Copper(l) ( Cuprous ) Chlorate Cyanide Gold(l) Hydroxide Hydrogen Hydride Hydrogen Carbonate ( Bicarbonate ) Iodide Mercury(l) ( Mercurous ) Nitrate Nitrite Permanganate Potassium Sodium Silver Barium Calcium Copper(ll) Carbonate Cobalt Chromate ( Cupric ) Dichromate Iron(ll) ( Ferrous ) Magnesium Manganate Mercury(ll) ( Mercuric ) Oxide Oxalate Sulphide Sulphite Sulphate Zinc Aluminium Arsenate Borate Chromium SYMBOL (NH4)+ (C103)- (HC03)- (N03)- (N02)- (Mn04)- Ba2+ ca2+ cu2+ (C03)2 (Cr04)2 (Cr207)2 Fe2+ Mg2+ (Mn04)2 Hg2+ 02 (C204)2 (S03)2 (S04)2 zn2+ (As03)3- (B03)3 cr3+ VALENCY 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3
  6. Gold(lll) Iron(lll) ( Ferric ) Nitride Phosphide Phosphate Fe3+ p3 pod- SYMBOLS OF SOME ELEMENTS 3 3 3 3 SYMBOL S.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 ELEMENT Aluminium Argon Antimony Barium Boron Bromine Beryllium Bismuth Calcium Chlorine Cobolt Copper Carbon Chromium Fluorine Gold Hydrogen Helium Iodine Iron Krypton Lead Lithium Magnesium Manganese Molybdinum Mercury Neon Nitrogen Nickel Oxygen Potassium Phosphorus Palladium SYMBOL Sb Be Ca co cu c Cr He pb Mg o p pd S.No. ELEMENT
  7. 35 36 37 38 39 40 41 42 43 44 45 S.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Platinum Silicon Silver Sodium Strontium Sulphur Tungsten Tin Uranium Vanadium Zinc pt Si Sr S w Sn Zn ATOMIC MASS OF FEW ELEMENTS ELEMENT Aluminium Argon Antimony Barium Boron Bromine Beryllium Bismuth Calcium Chlorine Cobolt Copper Carbon Chromium Fluorine Gold Hydrogen Helium Iodine Iron Krypton Lead Lithium Magnesium Manganese Molybdinum Mercury SYMBOL 27 40 35.5 63.5 12 1 4 56 24 S.No. ELEMENT SYMBOL
  8. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 S.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Neon Nitrogen Nickel Oxygen Potassium Phosphorus Palladium Platinum Silicon Silver Sodium Strontium Sulphur Tungsten Tin Uranium Vanadium Zinc 14 16 39 31 23 32 ATOMICITY OF FEW ELEMENTS ELEMENT Aluminium Argon Antimony Barium Boron Bromine Beryllium Bismuth Calcium Chlorine Cobolt Copper Carbon Chromium Fluorine Gold Hydrogen Helium Iodine Iron Lead Lithium SYMBOL 1 2 2 2 1 2 S.No. ELEMENT SYMBOL
  9. 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Magnesium Manganese Molybdinum Mercury Neon Nitrogen Nickel Oxygen Ozone Potassium Phosphorus Palladium Platinum Silicon Silver Sodium Strontium Sulphur Tungsten Uranium Vanadium Zinc 2 2 3 4 8

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