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Element A pure substance that cannot be broken down into simpler substances by physical or chemical means by hcj


A pure substance that
cannot be broken down
into simpler substances by
physical or chemical means.
Elements are considered pure…
…because all of the particles are identical.

                             The smallest
                             possible particle
                             of an element is
                             called an atom
                             of that element.
    How are elements found?
• Some elements are found in nature in
  their pure, natural form. (Gold &
• Other elements are chemically and/or
  physically combined with other
  elements in nature and need to be
  separated from the other elements to
  get a pure sample.
Scientists made a list of all the known elements
 and organized it on a chart (table) called the
        Periodic Table of the Elements.

         Periodic Table of Elements
    If it is an element, it is on the table
                   Periodic Table of Elements

If it is not an element, it is not on the table (chart).
 Element Names and Symbols
• Some element names match their symbol
  –   Hydrogen (H)
  –   Helium (He)
  –   Oxygen (O)
  –   Carbon (C)
• Other Elements do not seem to match their
  symbol at all.
  – Gold (Au)
  – Silver (Ag)
  – Mercury (Hg)

• This is because their symbol matches their
  name from a different language.
  – Gold is Aurum in Latin so the Au matches it’s Latin
  – Silver is Argentium in Latin so the Ag matches it’s
    Latin name.
  – Mercury is Hydragyrm in Latin so the Hg matches it’s
    Latin name.
  Scientists from all over the world use the same
 symbols and the same Periodic Table even if they
   have different common names for elements.

The symbol for gold is always (Au) even if its
 common name is:
  – Oro in Italian             - Kin in Japanese
  – Or in French               - Jin l in Chinese
  – Guld in Swedish            - Geum in Korean
  – Zloto in Polish            - Thongkam in Thai
  – Auksas in Lithuanian       - Emas in Indonesian
  – Dhahab in Arabic           - Kulta in Finnish
  – Zahaz in Hebrew            - Chrysos in Greek
• The smallest possible particle of an
  element is called an atom of that element.
•A pure substance made of two or
 more elements that are chemically
•This new substance usually has very
 different properties than the original
 elements combined to form it.
•Each particle of a compound is called
 a molecule of that compound.
      Examples of Compounds
• Water (H20) is made of two parts Hydrogen
  and one part Oxygen.
• Hydrogen is a clear gas that is highly volatile
  and explodes if placed near a flame.
• Oxygen is a clear gas that reacts with many
  substances and is required for most things to
• When chemically combined they form water
  which is a clear liquid that will not burn and
  does not react with many substances.
           H2O molecules
• Hydrogen (white)   Again, it is a
• Oxygen (purple)    pure substance
                     and all the
                     particles are
                     identical to each
                     other. But, each
                     particle is made
                     of more than one
  Table Salt (Sodium Chloride) NaCl
• Table salt is made of one part sodium and
  one part chlorine.
• Sodium (Na) is a silver solid that burns
  violently when it touches water.
• Chlorine (Cl) is a yellowish gas that is so
  poisonous that it is illegal to use in war.
• When Chemically combined they form the
  compound sodium chloride (NaCl) which is
  table salt, a white solid that is edible.
           NaCl molecules
• Sodium (purple)
• Chlorine (green)
• When two or more compounds or elements are
  physically (but not chemically) combined.
• The original substances keep their properties and
  no new substances are created
• They can be separated by physical means.
• They are considered “not pure substances”.
       Examples of Mixtures
• Sugar water - When sugar is mixed with
  water, the sugar and the water keep their
  properties because they still exist.
• The mixture can be separated by physical
      Identify each as an element,
         compound or mixture.

Element                     Compound

        Chemical Symbols
• Each element has its own symbol
• These symbols always begin with a
  capital letter
• If they have a second or third letter
  they are always lower case
      C for Carbon
      O for Oxygen
      Co for Cobalt
       Chemical Formulas
• The symbol for a compound is
  composed of more than one chemical
• The chemical formula for carbon
  dioxide is CO2.
• This means that a molecule of carbon
  dioxide is composed of one atom of
  carbon and two atoms of oxygen
       Chemical Equations
• A chemical equation is a set of
  symbols that describes what is
  occurring in a chemical reaction.
• In the equation    Na + Cl à NaCl
  Na (sodium) and Cl (chlorine) are the
  reactants and NaCl (salt) is the
    Reactants and Products
• The reactants are the substances
  that you have originally, before
  the chemical change and the
  products are what is created
  during the chemical change.
 Organization of the Periodic Table
• The periodic table is organized into
  families based on their similar properties
  of reactivity.
• Elements in the same vertical column will
  react similar when combined with a
  specific element.
• Example: Sodium reacts with Chlorine to
  produce salt (NaCl). Lithium and Bromine
  will react similarly with Chlorine.

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