Elements_ Compounds_ and Molecules

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					Elements, Compounds, and

• Elements
• Compounds
• Mixtures
• All matter in the universe is made from about
  100 different substances, called elements.
• Elements are called the building blocks of
  matter because all matter is composed of
• Each element is made up of the same type of
• A compound is a substance made of two or more
  different kinds of elements chemically combined in a
  specific ratio.
• Each compound is represented by a formula that
  uses symbols to identify which elements are present.
• A formula shows the ratio of elements in the
• H2O – ratio of Hydrogen is 2:1 Oxygen
• The symbols make up the formula. A formula
  is just chemical shorthand for the compound.
•      The subscript lets us know how many
  atoms are present.
•      The coefficient lets us know how many
  molecules are present.

• 6H2O + 6CO2 + energy     C6H12O6 + 6O2 + (ATP)
• A molecule is formed when two or more
  atoms join together chemically.

• Diatomic molecules are made of two atoms of
  the same element.

• Hydrogen – H2
• Oxygen – O2
What is the difference between a compound
              and a molecule?
• A molecule is formed when two or more
  atoms join together chemically.

• A compound is a molecule that contains at
  least two different elements.
• All compounds are molecules but not all
  molecules are compounds.
• Molecular hydrogen (H2), molecular oxygen
  (O2) and molecular nitrogen (N2) are not
  compounds because each is composed of a
  single element.
• Water (H2O), carbon dioxide (CO2) and
  methane (CH4) are compounds because each
  is made from more than one element.
• Most matter in the
  universe is found in
• A mixture is made from
  two or more substances
  either elements,
  compounds or both -
  that are not chemically

• Homogeneous mixture: is a substance in
  which two or more substances are uniformly
  spread out. For example salt water.
• Solution is another term for homogeneous
• Solute is the substance being dissolved.

• Solvent is the substance that dissolves a

• Solubility is the amount of a substance
  (solute) that will dissolve in a solvent.
• Salt water:

• The water is the solvent

• NaCl is the solute
        Heterogeneous Mixture
• A mixture in which different materials can be
  easily distinguished.

• Pizza, dry soup, chex mix, trail mix are all
       Colloids and Suspensions
• A colloid is a heterogeneous mixture that like
  a solution never settles. Milk and smoke are

• One way to tell a colloid from a solution is
  because milk is appears white because its
  particles scatter light. Called the Tyndall
• A suspension is a heterogeneous mixture
  containing a liquid in which visible particles

• River water
                    Mixtures and
                 compounds differ in
                     two ways…

 Substances in a mixture keep their
        individual properties.
Parts of a mixture are not necessarily
      present in specific ratios.
• A compound has properties different than the
  elements that make it up.

• The parts of a compound are present in
  specific ratio’s.
       Compounds and Mixtures
• Most of the matter around you is in the form
  of compounds or mixtures.

• Water, carbon dioxide, salt, vinegar, baking
  soda, lye, sugar, gasoline, and bleach are all
  chemical compounds.
NaCl is the formula for salt
               Water is H2O
• An oxygen atom can bond with
  two hydrogen atoms to make a
  molecule we call water. Water is
  an example of a compound,
  because it contains more than
  one kind of atom. The formula
  for water is H2O, meaning there
  are two hydrogen atoms for
  each oxygen atom.
         Carbon Dioxide CO2
• Carbon dioxide molecules are made from one
  carbon and two oxygen atoms joined together
  by covalent bonds. The chemical symbol is
Glucose - C6H12O6
• When a compound is broken down into its’ smallest
  piece it is called a molecule. You should be able to
  write the formula for the following:

• Water

• Oxygen

• Carbon Dioxide
• Is a large molecule made up of carbon,
  hydrogen, nitrogen, oxygen, and phosphorous.
       Kinetic theory of matter
• The idea that all matter is made up of
  constantly moving tiny particles.
 So, how do the atoms of elements come together
          to form compounds anyway??

• Elements form compounds to try to fill their
  outer energy level with valence electrons.

• This is called chemically stable. If the atom is
  not chemically stable it will lose, share, or gain

• A chemical bond is the force that holds
  together the atoms in a substance.
•   An Ion is an atom or group of atoms that
    has become electrically charged.
•    When an atom loses an electron it loses a
    negative charge and becomes a positive
•   When an atom gains an electron, it gains a
    negative charge and becomes a negative
        Forming an Ionic Bond:
• . Sodium has one valence electron and
  transfers that electron to chlorine
• Na + Cl- the negative and positive electrical
  charges attract each other so the oppositely
  charged ions come together and form sodium
  chloride (salt).
•   An ionic bond is the attraction between two
    oppositely charged ions. This attraction is
    similar to the attraction between opposite
    poles of two magnets.
•   .
• When two ions come together the opposite
  charges cancel out.
• Compounds are electrically neutral. When the
  ions come together they do so in a way that
  balances out the charges on the ions
    Molecules and Covalent Bonds

•      The attraction that forms between atoms
    when they share electrons is known as a
    covalent bond.

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