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Elements and Compounds



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  • 1. Elements and Compounds A Mr. Mularella Presentation
  • 2. The 4 Ancient Elements Earth Fire Air Water
  • 3. Elements
    • There are currently 118 elements that have been identified though only 88 of them are naturally occurring.
  • 4. Elements in the Universe
    • In our universe, hydrogen makes up 75% of all matter!
    • Helium makes up about 20% with oxygen being the 3 rd most abundant element.
    • All of the other elements are relatively rare in the universe.
  • 5. Elements in the Earth
    • In the Earth’s crust, oxygen is the most abundant element (46.6%).
    • Silicon is the second most abundant element (27.7%).
    • Aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%). and magnesium (2.1%) complete the list of elements that account for approximately 98.5% of the total mass of the earth's crust.
  • 6. Elements
    • Elements are a pure substance.
      • Made of only one kind of material, has definite properties, and is the same all throughout.
    • Elements are the simplest pure substance.
      • They cannot be broken down into simpler substances without losing their identity.
  • 7. Elements and Atoms
    • The smallest particle of an element that has the properties of that element is called an atom .
    • Atoms: the building blocks of matter.
    • Atoms of the same element are alike; atoms of different elements are different.
  • 8. Chemical Symbols
    • Shorthand way of representing the elements.
    • Usually one or two letters.
    • Usually taken from the name of the element.
      • Carbon-C, Calcium-Ca, Hydrogen-H, Iodine-I, Oxygen-O, Chlorine-Cl
  • 9. Chemical Symbols
    • Some symbols come from their Latin name:
      • Gold-Au--aurum
      • Silver-Ag--argentum
      • Iron-Fe--Ferrum
      • Mercury-Hg--hydrogyrum
  • 10. Compounds
    • Pure substances made up of more than one element.
    • 2 or more elements chemically combined.
    • Ex: H 2 O, NaCl, C 6 H 12 O 6 , CO 2
    • Unlike elements, compounds can be broken down to simpler substances.
    • This can happen through a chemical reaction.
  • 11. Compounds
    • The properties of the elements that make up a compound are often quite different from the properties of the compound itself.
      • Sodium-Na--highly reactive metal
      • Chlorine-Cl--poisonous gas
      • Sodium Chloride-NaCl--table salt
  • 12. Molecules
    • Compounds are made of molecules.
      • A molecule is 2 or more atoms chemically bonded.
      • Water-2 atoms of hydrogen and one atom of oxygen-together they form one molecule of H 2 O.
    • A molecule is the smallest particle of a compound that has all the properties of that compound.
    • Just as all atoms of a certain element are alike, all molecules of a certain compound are alike.
  • 13. Chemical Formulas
    • A shorthand way of representing compounds.
    • If chemical symbols are the “letters,” these are the “words.”
    • Ex: NH 3 - ammonia, C 3 H 7 OH - rubbing alcohol
    • Sometimes, the formula represents a molecule of a single element.
    • These are called diatomic molecules. This is how that element is naturally found.
      • O 2 -Oxygen H 2 -Hydrogen Cl 2 -Chlorine
  • 14. Chemical Formulas
    • Subscripts are small numbers used in chemical formulas.
    • They are placed to the lower RIGHT of the chemical symbols.
    • Represent # of atoms of an element in a compound.
    • CO 2 = 1 atom of carbon and 2 atoms of oxygen.
    • H 2 SO 4 = 2 atoms of hydrogen, 1 atom of sulfur and 4 atoms of oxygen