Chapter 3:Atoms and the Periodic Table

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Chapter 3Atoms and the Periodic Table

• Section 1 and 2

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Bell Ringer

• Name the following elements and give their atomic
  number

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Atoms

• Smallest particle
• Neutrons
• Protons
• Electrons

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Atoms

• Unreacted atoms have no overall charge.
• Although atoms are mode of charged particles,
  they do not have an overall charge because they
  have an equal number of protons and electrons
  whose charges cancel

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Electrons

• Exist in energy levels
• The number of filled energy levels an atom has
  depends on the number of electrons

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Energy Levels

• Electrons are found in orbitals within energy
  levels
• An orbital is a region in an atom where there is
  a high probability of finding electrons
• A s orbital is shaped like a sphere
• A p orbital is dumbbell shaped and can be
  oriented three different ways in space

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Orbitals

• Every atom has between one and eight valence
  electrons
• Valence electrons are found in the outermost
  shell of an atom and determine the atoms
  chemical properties
• Valence electrons are the electrons in an atom
  that participate in chemical bonding

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Bell Ringer

• Name the following elements and give their atomic
  number

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Chapter 4-Atoms and the Periodic Table

• Section 2 A Guided Tour of the Periodic Table

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Objectives

• Relate the organization of the periodic table to
  the arrangement of electrons within an atom
• Explain why some atoms gain or lose electrons to
  form ions
• Determine how many protons, neutrons, and
  electrons an atom has given its symbol, atomic
  number and mass number
• Describe how the abundance of isotopes affects an
  elements average atomic mass

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Organization of the periodic table

• The periodic table groups similar elements
  together.
• This organization makes it easier to predict the
  properties of an element based on where it is in
  the periodic table.
• Elements are listed in order of number of
  protons, because the periodic law states that
  when elements are arranged this way, similarities
  in their properties will occur in a regular
  pattern

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Organization of the periodic table

• The periodic table helps determine electron
  arrangement.
• Horizontal rows in the periodic table are called
  periods.
• Just as the number of protons an atom has
  increases as you move from left to right across a
  period, so does its number of electrons.

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Organization of the periodic table

• Elements in the same group have similar
  properties.
• A group is a vertical column of elements in the
  periodic table.
• Atoms of elements in the same group have the same
  number of valence electrons, so these elements
  have similar properties.

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Atoms Ions

• An ion is an atom or group of atoms that has lost
  or gained one or more electrons and has a
  negative or positive charge.
• A lithium atom loses one electron to form a 1
  charged ion
• A fluorine atom gains one electron to form a 1-
  charged ion

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How do the structures of Atoms Differ?

• The atomic number, Z, of an atom equals the
  number of protons in the nucleus.
• The mass number, A, of an atom equals the number
  of protons plus the number of neutrons in the
  nucleus.

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Atomic Number
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Mass Number
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How do the structures of Atoms Differ?

• An isotope is an atom that has the same number of
  protons as other atoms of the same element but
  have a different number of neutrons.
• Example Hydrogen has three isotopes, shown below.

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How do the structures of Atoms differ?

• If you know the atomic number and mass number of
  an atom, you can calculate the number of
  neutrons it has.
• Example uranium-235 has a mass number of 235.
  Like all uranium atoms, it has an atomic number
  of 92. The number of neutrons it has is
  therefore
• Mass number (A) 235
• Atomic number (Z) 92
• Number of neutrons 143

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Isotope
Another common form isotopes are written in
is Chlorine-35 or Chlorine-37
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Atomic Mass Unit

• Because the mass of a single atom is so tiny,
  atomic masses are usually expressed in atomic
  mass units.
• An atomic mass unit (amu) is equal to one twelfth
  of the mass of a carbon-12 atom.
• The average atomic mass for an element is a
  weighted average of the masses of all
  naturally-occurring isotopes of an element.

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Homework

• Section 2 Review
• Problems 1-8
• Page 119
• Study the first 30 elements of the periodic table

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Bell Ringer

• Find the number of protons, electrons and
  neutrons for the following isotopes
• Oxygen-18
• Sulfur-38
• Iron-56
• Uranium-239
• Potassium-41
• Tungsten-163

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Section Two Quiz

• Elements in the same horizontal row, or period,
  have the same number of valence electrons and
  similar chemical properties.
• True or False.
• What is an ion?
• How are isotopes of an atom different from one
  another?
• What unit is commonly used to express atomic
  masses?

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Chapter 4-Atoms and the Periodic Table

• Section 3 Families of Elements

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Objectives

• Locate alkali metals, alkaline-earth metals, and
  transition metals in the periodic table
• Locate semiconductors, halogens, and noble gases
  in the periodic table
• Relate an elements chemical properties to the
  electron arrangement of its atoms

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How Are Elements Classified?

• The elements are classified into three groups.
• Most elements are metals, elements that are shiny
  and conduct heat and electricity well.
• Nonmetals, all except hydrogen of which are found
  on the right side of the periodic table, may be
  solids, liquids, or gases at room temperature.
• Between these groupings are semiconductors,
  elements that can conduct electricity under
  certain conditions.

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How Are Elements Classified?

• The periodic table below shows the distribution
  of metal, nonmetals, and semiconductors in the
  periodic table.

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Metals

• The alkali metals, found in Group 1 of the
  periodic table, are very reactive.

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Metals

• The alkaline-earth metals, whichinclude calcium,
  are found in Group 2 of the periodic table, and
  are somewhat less reactive than the alkali
  metals.

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Metals

• The transition metals, such as gold, iron, and
  mercury, occupy Groups312 of the periodic
  table.

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Nonmetals

• Carbon is found in three different forms and can
  form many compounds.
• Nonmetals and their compoundsare plentiful on
  Earth.

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Nonmetals

• Semiconductors are intermediateconductors of
  heat and electricity
• Silicon is the most familiar semiconductor
• Silicon is an important part of computer chips,
  as well as other semiconductor devices such as
  transistors, LED display screens, and solar cells

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Halogens and Noble Gases

• Halogens, such as chlorine, are located in Group
  17
• Noble gases, such as neon, make up Group 18 and
  are unreactive

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Classwork

• Section 3 Review
• Problems 1-8 on page 128

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Homework

• Study for quiz on the first 30 elements

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Bellringer

• List three nonmetals and tell what they are used
  for
• List three metals and tell what they are used for

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Chapter 4-Atoms and the Periodic Table

• Section 4 Using Moles to Count Atoms

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Objectives

• Explain the relationship between a mole of a
  substance and Avogadros constant
• Find the molar mass of an element by using the
  period table
• Solve problems converting the amount of an
  element in moles to its mass in grams, and vice
  versa

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Counting Things

• There are many different counting units for
  example, eggs are packaged by the dozen.
• The mole is useful for counting small particles.
• A mole (abbreviation mol) is the number of
  particles that is the same as the number of atoms
  of carbon in 12 g of carbon-12.
• Avogadros constant is the number of particles
  per mole of a substance 6.022 1023

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Counting Things

• Moles and grams are related.
• The mass in grams of 1 mol of a substance is
  called its molar mass.
• For example, 1 mol of carbon-12 atoms has a molar
  mass of 12.00 g.
• The molar mass of an element is its average
  atomic mass, which is listed in the periodic
  table.

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Calculating with Moles

• To convert between moles and grams and vice
  versa, you can use a conversion factor a ratio
  that is derived from the equality of two
  different units.
• Lets say that a shopkeeper knows that exactly
  10 gumballs have a total mass of 21.4 g. This
  relationship can be written as either one of two
  equivalent conversion factors

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Math Skills

• Using your conversion factor
• What is the mass of exactly 50 gumballs?

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Calculating with Moles

• An elements molar mass can be used as a
  conversion factor.
• The diagram below shows how to set up the
  conversion factor, depending on whether you want
  to convert from amount to mass or the other way
  around.

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Math Skills

• Converting Amount to Mass
• Determine the mass in grams of 5.5 mol of iron

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Math Skills

• Converting Mass to Amount
• Determine the amount(mol) of iron present in
  352g of iron

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Classwork

• Practice Problems 1-3 page 132
• Practice Problems 1-4 page 133
• HOMEWORK
• Section 4 Review
• Problems 1-9
• Page 134
• Study for Quiz