Honors Intergraded II

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Honors Intergraded II

• Chapter 3 Atoms and the Periodic Table

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Atomic Structure

• Atoms are tiny units that determine the
  properties of all matter.
• Our understanding of atoms required many
  centuries.
• 4th Century BC Greek philosopher Democritus
  suggested that the universe was made of invisible
  units called atoms.
• Atom -Greek word means unable to be divided.

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• Atoms are the building blocks of molecules.
• 1808 English schoolteacher John Dalton proposed
  his own atomic theory.
• Every element is made of tiny unique particles
  called atoms that cannot be subdivided.
• Atoms of the same element are exactly alike.
• Atoms of different elements can join to form
  molecules.

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• An atom is the smallest part of an element that
  still has the element's properties.
• What is an Atom?
• 100 years after Dalton published his theory,
  scientist determined that atom could be split.
• Atoms are made of protons, neutrons, and
  electrons.
• J.J. Thomson discovered electrons
• Rutherford discovered the nucleus of the atom.

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• Center of the atom is small dense nucleus with a
  positive electrical charge.
• The nucleus is made of protons (positive charge)
  and neutrons (no charge) they are almost
  identical is size and mass.
• Moving around outside the nucleus and encircling
  it is a cloud of very tiny negatively charged
  subatomic particles with very little mass these
  are the electrons.

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• Atoms have no overall charge.

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Models of the atoms

• Bohr's model compares electrons to planets.
  Neils Bohr (1913) Danish said that electrons
  travel in paths like energy levels.
• According to modern theory, electrons behave more
  like waves. This replaced Bohr's model in 1925.

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• All the electrons energy levels is a region
  called electron cloud.
• Electrons are found in orbits within energy
  levels.
• The regions in an atom where electrons are found
  are called orbitals.
• Electrons may occupy 4 different kinds of
  orbitals within atoms.

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• s orbital -2 electrons, simplest kind, lowest
  energy, shaped like a sphere
• p orbital -6 electrons total, dumbbell shaped,
  oriented three different ways in space with 2
  electrons each
• d orbital - 10 electrons total, more complex, 5
  possible orbital 2 electrons each
• f orbital -14 electrons total, greatest energy,
  more complex, 7 possible orbital 2 electron each

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• Every atom has one or more valence electrons.
• An electron in the outer most energy level of an
  atom is called a valence electron.

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Organization of the Periodic Table

• The periodic table groups similar elements
  together.
• Elements are represented by their symbols.
• Elements are arranged in order based on the
  number of protons.
• This was discovered by Moseley.
• The first periodic table was based on mass by
  Mendelevee.

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• Elements are listed in this order in the periodic
  table because the periodic law states that when
  elements are arranged this way, similarities in
  their properties will occur in a regular pattern.
• Using the periodic table to determine electronic
  arrangement, horizontal rows in the periodic
  table are called periods.
• Vertical column of elements in the periodic table
  is group or family.

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• Elements in the same group have similar
  properties.

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Some Atoms Form Ions

• Atoms that do not have filled outermost energy
  levels may undergo a process called ionization.
• They may gain or lose valence electrons so that
  they have a full outermost energy level.
• If an atom gains or loses electrons it no longer
  had the same number of electrons as it does
  protons.
• An ion is then formed.
• An ion is an atom or group of atoms that has
  lost or gained one or more electrons and
  therefore has a net electric charge.

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• A lithium atom loses one electron to form a 1
  charged ion.
• Removing an electron forms a positive ion called
  a cation.
• A fluorine atom gains one electron to form a 1-
  charged ion.
• The gaining of electrons form a negative ion or
  anion.

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How Do the Structures of Atoms Differ?

• Atomic number equals the number of protons.
• Number of protons equals the number of electrons.
  
• The largest naturally occurring atom uranium has
  92 protons.
• The atomic number for a given element never
  changes.

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• Mass number equals the total number of subatomic
  particles in the nucleus, protons plus neutrons.
• Isotopes of an element have different numbers of
  neutrons but the same number of protons.
• Hydrogen has three isotopes.
• Some isotopes are more common than others are.

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• Calculating the number of neutrons in an atom the
  mass number (protons plus neutrons) subtract the
  atomic number (protons) gives the number of
  neutrons.
• Quick Activity page 84

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• The mass of an atom is expressed in atomic mass
  units (amu).
• An atomic mass unit is equal to 1/12 of the mass
  of a carbon 12 atom.
• Protons and neutrons have a mass of about 1.0
  amu.
• Average atomic mass is the weighted average of
  the masses of all naturally occurring isotopes of
  an element.

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Families of Elements

• Have many chemical and physical properties in
  common because they have the same number of
  valence electrons.

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How Are Elements Classified

• Metals
• Nonmetals
• Semiconductors or metalloids

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• Metals are shiny solids that can be stretched and
  shaped good conductors of heat and electricity.
• Nonmetals except for hydrogen are found on right
  side of periodic table.
• Found as solids, liquids, or gases. Solid
  nonmetals typically are dull and brittle.
• Poor conductors of heat and electricity.
• Some elements that are classified as nonmetals
  can conduct under certain conditions.
• These elements are sometimes considered to be
  their own group and are called semiconductors or
  metalloids.

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Metals

• Many elements
• 4 different kinds of metals
• Two groups to the left
• Tin, lead, aluminum located on the right
• Most metals in the middle

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Alkali metals Group 1

• Soft shiny and reacts violently with water
• Must be stored in oil to prevent it from reacting
  with moisture in the air
• Has one valence electron
• Forms positive ions with a 1 charge

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Alkaline Earth Metals Group 2

• Two valence electrons
• Less reactive than alkali metals
• Form positive ions with a 2 charge

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Transition Metals (those in the middle)

• Located in groups 3-12
• Less reactive
• Form positive ions (can produce more than one)
• Conduct heat and electricity
• Stretched and shaped without breaking
• Ductile pulled into wires
• Malleable hammered into sheets

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• Technetium and promethium are synthetic elements
• Man made and radioactive
• Last two rows of transition metals are sometimes
  called rare earth elements.
• All elements with atomic number greater than 92
  are man made.

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Nonmetals

• Carbon is found in 3 different forms and can also
  form compounds
• graphite
• diamond
• fullerness confirmed in 1990

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• Nonmetals and their compound are plentiful on
  earth
• Halogens Group 17
• Form negative ion 1-
• Noble Gases Group 18
• Inert or unreactive
• Outer energy level is full of electrons

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Semiconductors or Metalloids

• Boron extremely hard element
• Silicon 28 of earth crust
• Germanium
• Arsenic shiny solid that tarnishes when exposed
  to air
• Antimony bluish white brittle solid that shines
• Tellurium silvery white solid
• These have properties of both metals and nonmetals

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Using Moles to Count Atoms

• The mole is useful for counting small particles.
  
• Mole (mol) the SI base unit that describes the
  amount of a substance.
• A mole is a collection of a very large number of
  particles.
• This number is usually written as 6.022 x 10 23/
  moles and is referred to as Avogadro's constant.

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• Moles and grams are related. The mass in grams
  of 1 mol of a substance is called its molar mass.
• Calculating with Moles
• Conversion factors a ratio to one that expresses
  the same quantity in two different ways.
• Practice Conversion Factors page 98 1-3
• Relating moles to grams
• Practice Converting Amount to Mass page 99 1-4