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Ionic%20Bonding%20(6.1)

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Ionic Bonding (6.1) Review Valence Electron - an electron that is in the highest occupied energy level of an atom Key role in chemical reactions The number of the ... – PowerPoint PPT presentation

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Title: Ionic%20Bonding%20(6.1)


1
Ionic Bonding(6.1)
2
Review
  • Valence Electron - an electron that is in the
    highest occupied energy level of an atom
  • Key role in chemical reactions
  • The number of the group matches the number of
    valence electrons
  • Elements in a group have similar properties
    because they have the same number of valence
    electrons

3
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4
Stable Electron Configurations
  • When the highest occupied energy level of an atom
    is filled with electrons, the atom is stable and
    not likely to react
  • Nobel gases have stable electron configurations
    with eight valence electrons (helium only has
    two)
  • The chemical properties of an element depend on
    the number of valence electrons

5
  • Electron Dot Diagram
  • Model of an atom in which each dot represents a
    valence electron
  • The symbol at the center represents the nucleus
    and all other electrons in the atom

6
Ionic Bonds
  • Some elements achieve stable electron
    configurations through the transfer of electrons
    between atoms

7
Transfer of Electrons
  • Chlorine is one electron short of having 8
    valence electrons
  • Sodium has one too many electrons to be stable
  • Sodium transfers its extra electron to chlorine
    to make both atoms more stable

8
Formation of Ions
  • When an atom gains or loses electrons its charge
    is no longer neutral
  • Ion - an atom that has a net positive or negative
    electric charge
  • Anion - an ion with a negative charge
  • Named by using part of the element name plus the
    suffix -ide
  • Example Cl- is called a chloride ion
  • Cation - an ion with a positive charge
  • Named by using the element name
  • Example Na is called a sodium ion

9
  • When an anion and cation are close together the
    form chemical bonds because opposite charges
    attract
  • Chemical Bond - the force that holds atoms or
    ions together as a unit
  • Ionic Bond -the force that holds cations and
    anions together
  • Form when electrons are transferred from one atom
    to another

10
Ionization Energy
  • Amount of energy used to remove an electron from
    an atom of an element
  • The energy allows the electrons to overcome the
    attraction of the protons in the nucleus
  • Varies from element to element
  • The lower the ionization energy, the easier it is
    to remove an electron from an atom

11
Ionic Compounds
  • Compounds that contain ionic bonds
  • Chemical Formula - a notation that shows what
    elements a compound contains and the ratio of
    atoms or ions of these elements in the compound
  • Examples
  • Sodium chloride is NaCl
  • Magnesium chloride is MgCl2

Subscript is used to show the relative numbers of
atoms of the elements present. If there is only
one atom of an element in the formula no
subscript is used
12
Crystal Lattices
  • Repeating pattern of ions in fixed positions
  • Crystals - solids whose particles are arranged in
    a lattice structure
  • Classified into groups based on the shape of
    their crystals
  • The arrangement of the ions depends on the ratio
    of ions and their relative sizes

13
Properties of Ionic Compounds
  • The properties of an ionic compound can be
    explained by the strong attractions among ions
    within a crystal lattice
  • Properties
  • High melting point because of strong attractions
    between particles more energy needed to
    separate them
  • Poor conductor of electricity as solids because
    of the structure but good conductors as liquids
  • Crystals shatter when struck because the like
    charged ions repel each other
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