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    Basic Concepts of Chemical Bonding: Lewis Symbols - The Octet Rule

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    The document discusses basic concepts of chemical bonding including Lewis symbols, the octet rule, ionic bonding, and lattice energy. Lewis symbols represent valence electrons of atoms using dots to show how atoms gain, lose, or share electrons to achieve stable octets of eight valence electrons. Ionic bonding occurs through the transfer of electrons between metals and nonmetals to form cations and anions. Ionic compounds are stable due to the attractive forces between the opposite charges on the ions. Lattice energy describes the energy required to separate ions in an ionic solid.

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    Basic Concepts of Chemical Bonding: Lewis Symbols - The Octet Rule

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    The document discusses basic concepts of chemical bonding including Lewis symbols, the octet rule, ionic bonding, and lattice energy. Lewis symbols represent valence electrons of atoms using dots to show how atoms gain, lose, or share electrons to achieve stable octets of eight valence electrons. Ionic bonding occurs through the transfer of electrons between metals and nonmetals to form cations and anions. Ionic compounds are stable due to the attractive forces between the opposite charges on the ions. Lattice energy describes the energy required to separate ions in an ionic solid.

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    Ch 8

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    The document discusses basic concepts of chemical bonding including Lewis symbols, the octet rule, ionic bonding, and lattice energy. Lewis symbols represent valence electrons of atoms using dots to show how atoms gain, lose, or share electrons to achieve stable octets of eight valence electrons. Ionic bonding occurs through the transfer of electrons between metals and nonmetals to form cations and anions. Ionic compounds are stable due to the attractive forces between the opposite charges on the ions. Lattice energy describes the energy required to separate ions in an ionic solid.

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    58 views4 pages

    Basic Concepts of Chemical Bonding: Lewis Symbols - The Octet Rule

    Uploaded by

    Pineraser
    The document discusses basic concepts of chemical bonding including Lewis symbols, the octet rule, ionic bonding, and lattice energy. Lewis symbols represent valence electrons of atoms using dots to show how atoms gain, lose, or share electrons to achieve stable octets of eight valence electrons. Ionic bonding occurs through the transfer of electrons between metals and nonmetals to form cations and anions. Ionic compounds are stable due to the attractive forces between the opposite charges on the ions. Lattice energy describes the energy required to separate ions in an ionic solid.

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    Miles Eckles March 10, 2011

    Chem 101 A Chapter 8

    Basic Concepts of Chemical Bonding


    Lewis Symbols – The Octet Rule
     Valence electrons – electrons involved in chemical bonding, these are the electrons in
    the incompletely filled outer shell of the atom.
     Lewis symbols or electron dot symbols are a convenient way to show valence electrons
    of atoms and tracking them for bond formation.
    Example of Lewis Symbols
    ● ●
    Li● ●Be● ●B● ●C ●
    ●
    ● ● ●● ●●
    ●N●● ●● O ●● ●F●● ●●Ne●●
    ● ● ●● ●●

     If more than 3 valence electrons each side must have at least 1 electron on each side
    before a side can get 2 valence electrons

    Octet Rule
     Lewis noticed that Noble gases (except for Helium) all had eight valence electrons and
    were unreactive. Furthermore, many atoms undergoing reactions also end up with eight
    valence electrons
     OCTET RULE: atoms tend to gain, lose, or share electrons until they are surrounded by
    eight valence electrons.
    o an octet of electrons consists of full s and p subshells
    o Lewis symbols for an octet can be thought as four pairs of valence electrons
    Ionic Bonding
     Ionic bond – electrostatic forces that exist between ions of opposite charge. There is a
    literal transfer of electrons from a metal atom to a nonmetal atom to form cations and
    anions.
     Example:
    o 2Na (s) + Cl2 (g) → 2NaCl(s)
    Diagram

    ●●
    ● ●
    Cl
    Na ● ●
    ●●
    ●●
    ● ●
    Cl
    Na ● ●
    ●●

    Energetics of Ionic Bond Formation


     Ionic compounds are generally stable is the attraction of unlike charges.
     Lattice energy – the energy required to completely separate a mole of a solid ionic
    compound into its gaseous atoms.

    E=k Q1Q2 Lattice Energy Magnitude


    d

    Lattice energy magnitude


     K = 8.99 x 109 J–m/C2
     Q1 and Q2 are the charges on the ions
     d is the distance between the ions’ centers
     As ionic charge increases, so does the energy of attraction.
     As distance between centers decreases, lattice energy increases
    Example
     Rank the lattice energies of CaCl2, MgCl2, and NaCl from lowest to highest.
     NaCl must be lower than the others because its charges are 1+ and 1-, while the others
    are 2+ and 1-.
     The ionic radius of Mg 2+ is smaller than Ca2+, so Mg is closer to Cl than Ca
     NaCl < CaCl2 < MgCl2
    Electron Configuration and Ionic Charge State
     Na will lose 1 electron to become a stable OCTET, Na+.
     Cl will gain 1 electron to become a stable OCTET, Cl-.
     Thus, metals have 1+, 2+, 3+ charges as ions. Likewise, nonmetals from group VA, VIA,
    VIIA will have 3-, 2-, 1- charges as ions.
    Examples:
     What ions would be formed from: a) Ba, b) Al, c) O, d) P?

    o Ba2+ (group IIA)


    o Al3+ (group IIA)
    o O2- (group VIA)
    o P3- (group VA)
    Transition Metals Special Case
    Transition metals have d electrons; don’t follow the OCTET Rule.
    In forming ions, transition metals lose the valence-shell s electrons first, then as many d
    electrons are required to reach the charge of the ion.
    Example: Fe[Ar]3d64s2
    Losing two electrons, Fe2+ [Ar]3d6
    Losing one more, Fe3+ [Ar]3d5
    Polyatomic Ions
     Polyatomic ions like SO42- pr NH4+ as a group of atoms act as a charged species in forming
    an ionic compound with oppositely charged species.

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