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Elements and compounds
- 3. INTRODUCTION: • A substanceis pure from of matter. • In other words , a substance is matter than contains only one type of atom or molecule. • Atoms: All substances are made up of tiny particles. • Atom is made up of fundamental particles called Protons, Neutrons and electrons.
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- 5. ELEMENTS: • The substancewhich is made up of same kind of atoms is called an Element. • Chemical symbols are used to represents Elements. • It is the basic unit of matter and cannot be broken into two or more simpler substances.
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- 10. CHEMICAL SYMBOLS: • Itis difficult to mention the name of elements in all situations. Hence scientists have give symbols to denotes the elements. • Simple pictures used to denotes elements was started by Greeks. • Further continued by John Dalton. • Example: Circle was used to denote carbon. • J.J Berzilius replaced these pictures by symbols.
- 11. RULES FOR WRITINGSYMBOL OF ELEMENTS • Rule-1: the first letter of the name of an element in English used as its symbol. • Example: Carbon is represented as C, because C is the first letter of Carbon. • Iodine-I, Boron-B ,sulphur-S, Oxygen-O • Rule-2:if the name of two elements begin with the same letter then first two letters are taken. The first letter is always written in capital and second letter should be written small.
- 12. Continued…. • Example: Carbonand Cobalt, both begin with C then what should be the symbol of cobalt? • Answer: Cobalt-Co. • Aluminium-Al, Radium-Ra, Silicon-Si. • Rule-3:If the first two letters of the elements are the same then next prominent letter should be taken.
- 13. Continued….. • Example:Magnesium andManganese have the first two letters the same.In this case the symbol of Manganese is Mn and Magnesium is Mg. • Rule-4:Symbol of some elements are derived from their Latin. While writing symbols using Latin names. • Example: The elements sodium is called Natrium in Latin. Hence its symbol is Na. • Copper (Cuprum Latin name)-Cu • Silver(Argentum Latin name)-Ag
- 14. COMPOUNDS: • The substancewhich is made up of different types of atoms is called a COMPOUND. • A compound is formed by the combination of two or more elements. • Two or more elements combine in a definite ratio to form a compound. • Example: Water is a compound that contains oxygen and hydrogen. • Sodium chloride is a compound that contains sodium and chlorine.
- 15. MOLECULE: • Two ormore atoms are combined to form a MOLECULE.
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- 17. Example-2: • Molecule ofcarbon-di-oxide(CO2) is formed by combining one atom of carbon and 2 atoms of oxygen.
- 18. MOLECULAR FORMULA • Letus learn how to denote the molecules of compound. • A molecule of carbon-di-oxide is represented as CO2.Hence CO2 is called the molecular formula. • Definition: Symbolic representation of molecules of elements or compounds is called molecular formula.
- 19. EXAMPLES: Compound Constituent elements No. ofatoms & their ratio Molecular formula Hydrogen Chloride or Hydrochloric acid Hydrogen Chlorine 1 atom 1 atom 1:1 HCL Ammonia Nitrogen Hydrogen 1 atom 3 atoms 1:3 NH3 Water Hydrogen Oxygen 2 atoms 1 atom 2:1 H2O Potassium Permanganate Potassium Manganese Oxygen 1 atom 1 atom 4 atoms 1:1:4 KMnO2 Carbon-di-oxide Carbon Oxygen 1 atom 2 atoms 1:2 CO2
- 20. USES OF SYMBOLSAND MOLECULAR FORMULAE: • The name of the elements and compounds can be denoted in short forms which save time and place while writing. • Formula indicates the names of all the elements present in a compound. • The number of atoms present in the compound can be known easily by molecular formula.