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Elements and Compounds
 

Elements and Compounds

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    Elements and Compounds Elements and Compounds Presentation Transcript

    • Elements and Compounds A Mr. Mularella Presentation
    • The 4 Ancient Elements Earth Fire Air Water
    • Elements
      • There are currently 118 elements that have been identified though only 88 of them are naturally occurring.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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
    • Chemical Symbols
      • Some symbols come from their Latin name:
        • Gold-Au--aurum
        • Silver-Ag--argentum
        • Iron-Fe--Ferrum
        • Mercury-Hg--hydrogyrum
    • 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.
    • 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
    • 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.
    • 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
    • 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