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    The document discusses different types of chemical bonds and weak forces: 1) Polar covalent bonds involve unequal sharing of electron pairs, creating a partial charge separation. 2) Weak forces like hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions are not strong enough to bind atoms but influence molecular structure. 3) Hydrogen bonds form between hydrogen and electronegative atoms, van der Waals forces result from induced dipoles, while ionic and hydrophobic interactions involve charged and nonpolar groups respectively.

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    9 views12 pages
    The document discusses different types of chemical bonds and weak forces: 1) Polar covalent bonds involve unequal sharing of electron pairs, creating a partial charge separation. 2) Weak forces like hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions are not strong enough to bind atoms but influence molecular structure. 3) Hydrogen bonds form between hydrogen and electronegative atoms, van der Waals forces result from induced dipoles, while ionic and hydrophobic interactions involve charged and nonpolar groups respectively.

    Original Description:

    Some review question of physiology

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    The document discusses different types of chemical bonds and weak forces: 1) Polar covalent bonds involve unequal sharing of electron pairs, creating a partial charge separation. 2) Weak forces like hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions are not strong enough to bind atoms but influence molecular structure. 3) Hydrogen bonds form between hydrogen and electronegative atoms, van der Waals forces result from induced dipoles, while ionic and hydrophobic interactions involve charged and nonpolar groups respectively.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    9 views12 pages

    Review

    Uploaded by

    jannatul80002
    The document discusses different types of chemical bonds and weak forces: 1) Polar covalent bonds involve unequal sharing of electron pairs, creating a partial charge separation. 2) Weak forces like hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions are not strong enough to bind atoms but influence molecular structure. 3) Hydrogen bonds form between hydrogen and electronegative atoms, van der Waals forces result from induced dipoles, while ionic and hydrophobic interactions involve charged and nonpolar groups respectively.

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    Download as ppt, pdf, or txt
    of 12

    Review: some basic chemical

    words and concepts


    Polar Covalent Bonds and Electronegativity:

     Covalent bonds (between two different atoms) in which the


    sharing of the electron pair is unequal are called polar covalent
    bonds (electrons spending more time around the more
    nonmetallic atom).
     In such a polar covalent bonds there is a charge separation with
    one atom being slightly more positive and the other more
    negative, i.e., the bond will produce a dipole moment.
     The ability of an atom to attract electrons in the presence of
    another atom is a measurable property called electronegativity.
    +
    H H H O
    Weak chemical forces
    Covalent bonds hold atoms together so that molecules are formed.
    In contrast, weak chemical forces or noncovalent bonds are
    intramolecular or intermolecular attractions between atoms.

    • Hydrogen bonds
    • Van der Waals forces
    • Ionic interactions
    • Hydrophobic
    interactions
    None of these forces are strong enough to bind free atoms together.
    (typically range from 4 to 30 kJ/mol)
    Hydrogen bonds (H bonds)
    Hydrogen bonds Form between a hydrogen and a second electronegative
    atom
    Strength: 12~30 kJ/mol ; Distance: 0.3 nm

    H bonds are cylindrically symmetrical and tend to be highly directional,


    forming straight bonds between donor, hydrogen, and acceptor atoms.
    Van der Waals forces

    Van der Waals forces are the result of induced electrical interactions
    between closely approaching atoms or molecules as their negatively
    charged electron clouds fluctuate instantaneously in time.

    Strength: 0.4~4.0 kJ/mol ; Distance: 0.3~0.6 nm

    Strength depends on the relative size of the atoms or molecules and the
    distance between two molecules: The greater the area, the stronger the
    interaction.
    The sum of many such interactions within a macromolecule or between
    molecules can be substantial (accumulated).
    Ionic interactions

    Ionic interactions are the result of attractive forces


    between a positive charged group and a negative
    charged group (intramolecular or intermolecular).
    Strength: 20 kJ/mol ; Distance: 0.25 nm
    Strength also depends on the relative polarity of the
    interacting charged species.
    _
    NH3+ OOC
    Because the electrical charge is radially distributed, these
    interactions may lack the directionality of H bonds or the
    precise fit of van der Waals interactions.
    Hydrophobic interactions

     Hydrophobic interactions result from the strong tendency of


    water to exclude nonpolar groups or molecules

     Water molecules “exclude” hydrophobic molecules from aqueous


    solution and drive the tendency of nonpolar molecules to cluster
    together

     The formation of oil droplets in the water is an approximation of


    this phenomenon

     These tendencies have important consequences in the creation


    and maintenance of the macromolecular structures and
    supramolecular assemblies of living cells

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