Chemistry Concepts

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Chemistry Concepts

• What is matter?
• What are some phases of matter?
• What are some properties of matter?
• What does an atom look like?
• How do you use the periodic table to predict
  element behavior?
• What are chemical reactions?

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Matter

• Matter is anything that has mass and takes up
  space.
• Examples?
• Non-examples?
• All matter has properties or characteristics

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Properties of Matter

• Physical Properties
• Can be observed without changing the matters
  chemical composition.
• Examples
• Temperature
• Length
• Mass
• Physical State (gas, liquid, solid)

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Properties of Matter

• Chemical Properties
• Observed when matter changes into a new substance
• Examples
• Reactivity
• Flammability

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The Atom

• An atom is the smallest building block of matter.
• Atoms are made of neutrons, protons and
  electrons.
• The nucleus of an atom is extremely small in
  comparison to the atom. It contains the neutrons
  and protons.

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Atomic Particles

• proton
• Found in a nucleus with a positive charge. Number
  of these gives atomic number.
• neutron
• Found in the nucleus of an atom. It is almost
  identical in mass to a proton, but carries no
  electric charge.
• electron
• Found in the electron cloud surrounding the
  nucleus. This particle has a negative charge.

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Atomic Energy Levels

• The regions where electrons move are called
  energy levels because the electrons in the
  different regions have different amounts of
  energy.

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Energy Levels cont

• Each energy level can hold a fixed number of
  electrons.
• The 1st energy level can hold 2 e-
• The higher energy levels can hold up to 18 e-
  (usually 8e-)
• An atom with its outer energy levels filled with
  electrons are more stable than ones without their
  outer levels filled.

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Atoms Elements

• An element is a substance that cannot be broken
  down into a simpler substance by chemical means.
• An element is made up of only one type of atom.
• Atoms of different elements can bond together for
  form compounds.
• When elements bond together their chemical
  properties change.

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Characteristics of Elements

• Each element has different
• Atomic Number number of protons
• Mass Number number of protons plus the number
  of neutrons
• Physical Properties
• Chemical Properties

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Brief History of the Periodic Table

• German Lothar Meyer created a table that was an
  accurate (for the time) accounting of the known
  facts about each element, such as melting point
  and atomic volume. The table clearly showed the
  existence of periodic chemical families. In 1870
  Meyer's table and description of the periodic law
  was published.

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History continued

• A year earlier however, the 35 year old Mendeleev
  presented a much bolder and scientifically useful
  table. In it, the periodic relationship between
  chemical groups, that is, elements with a similar
  characteristics of reaction, is clearly
  illustrated. In a scientific triumph, gaps in the
  table accurately predicted undiscovered elements.
  

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Mendeleevs Table

• Although it is nearly 130 years old, Mendeleev's
  table differs little from the charts on the walls
  of laboratories today. The insight obtained in
  that productive decade resulted in a tool that
  furthers understanding and eases the use of
  chemistry in every laboratory in the world.

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Periodic Table of Elements

• The periodic table is organized like a big grid.
• If you have ever looked at a grid, you know that
  there are rows (left to right) and columns (up
  and down).
• The periodic table has rows and columns too, and
  they each mean something different.
• The elements are placed in specific places
  because of the way they look and act.
• The Periodic table is designed to help you
  predict what an element's physical and chemical
  properties are.
• You can also predict what elements will bond with
  each other.

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Organization of the Periodic Table

• When you look at the picture to the right, you
  can see that the rows are different colors. Even
  though they skip some squares in between, all of
  the rows go left to right.
• When you look at a periodic table, each of the
  rows are considered to be different PERIODS (Get
  it? Like PERIODic table)

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Organization cont

• In the periodic table, elements have something in
  common if they are in the same row. All of the
  elements in a period have the same number of
  atomic energy levels.
• Every element in the top row (the first period)
  has one level for its electrons. All of the
  elements in the second row (the second period)
  have two level for their electrons. It goes down
  the periodic table like that. At this time, the
  maximum number of levels is seven.
• Elements in a period are not alike in chemical or
  physical properties.

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Organization cont

• The columns in the Periodic Table are called
  GROUPS.
• You can know properties of a certain element by
  knowing which group it belongs to.
• The elements in a group have the same number of
  electrons in their outer shell.

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Organization cont

• Every element in the first column (group one) has
  one electron is its outer shell. Every element on
  the second column (group two) has two electrons
  in the outer shell. As you keep counting the
  columns and you'll know how many electrons are in
  the outer shell.
• The elements in between, with the grey color, are
  called TRANSITION elements. They have special
  electron rules.

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Reading the Periodic Table

• When you look at the periodic table, you
  should notice that each box represents a
  different element, and each box contains vital
  information about the element .

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Think inside the Box

• The top number is the atomic number. The atomic
  number tells how many protons are in one atom of
  that element. Since no two elements have the same
  atomic number, no two elements have the same
  number of protons.

6 C Carbon 12.011
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Thinking cont

• The large letter is the element's symbol, and
  just below that is the element's name. Each
  element has its own unique symbol and name.
• Below the name is the element's atomic mass.
• The atomic mass is the number of protons plus the
  number of neutrons.

6 C Carbon 12.011
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Chemical Reactions

• Let's start with the idea of a reaction. In
  chemistry, a reaction is when two or more
  molecules interact and something happens. That's
  it. What molecules are they? How do they
  interact? What happens? Those are all the
  possibilities in reactions. The possibilities are
  infinite.

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KEY POINT 1

• A chemical change must occur. You start with one
  compound and turn it into another. That's an
  example of a chemical change. A steel garbage can
  rusting. That rusting happens because the iron in
  the metal combines with oxygen in the atmosphere.
  A refrigerator or air conditioner cooling air is
  not a reaction... That is a physical change.

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KEY POINT 2

• It could be ions, molecules or pure atoms. We
  said molecules in the above section, but a
  reaction can happen with anything, just as long
  as a chemical change occurs (not a physical one).
  

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KEY POINT 3

• Single reactions often happen as part of a larger
  series of reactions. Take something as simple as
  the leaves changing color in the fall. A whole
  series of reactions (hundreds actually) are
  needed to make it happen.

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Bonding

• When atoms combine, it is called bonding.
• There are two types of bonds
• Ionic
• Covalent

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Ionic Bonds

• Sometimes, atoms will become more stable if they
  either gain or lose electrons.
• For example, the element chlorine becomes more
  stable when it gains an electron, and sodium
  becomes more stable when it loses an electron. If
  an atom of chlorine and an atom of sodium come
  near enough to one another, an electron from the
  sodium can actually jump to the chlorine atom.
  However, the sodium atom now has more protons
  than electrons, so it has a positive charge. The
  chlorine atom now has an additional electron and
  so has a negative charge. These charged atoms are
  called ions.
• Ions of opposite charges, like the sodium and
  chlorine ions, are attracted to one another in
  what is called an ionic bond.

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Covalent Bonds

• In other cases, two atoms will share the
  electrons so that each becomes more stable.
• For example, oxygen, which normally has eight
  electrons, happens to become more stable when it
  has two additional electrons. If two oxygen atoms
  come together, they can each contribute a pair of
  electrons to be shared by both atoms.
• This type of sharing is called a covalent bond.
• In the case of the oxygen atoms, the electrons
  are shared exactly equally. However, in most
  cases, one atom pulls on the electrons more than
  the other. In these bonds, one side of the
  molecule is slightly more negative since the
  negatively charged electrons are closer to that
  side. These molecules are said to be polar (water
  is an example), whereas molecules which share the
  electrons equally are nonpolar.

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Questions to Ponder

• What is matter and what are some of its
  properties?
• What are the differences between physical and
  chemical properties?
• What are the 3 atomic particles, where are they
  located and what are their charges and masses?
• What information about elements is in the
  periodic table?
• How can the arrangement of the periodic table
  help you make predictions about the chemical and
  physical properties of elements?
• Describe chemical reactions.
• Compare/Contrast ionic covalent bonds.