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Chemical Bond

Chemical Bond. Forms when 2 or more atoms rearrange valence electrons to increase stability Electrical attraction between the valence electrons of one atom and the nucleus of another. http://education.jlab.org/frost/electroscope.html. Episode 501. Ionic Bond.

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Chemical Bond

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  1. Chemical Bond • Forms when 2 or more atoms rearrange valence electrons to increase stability • Electrical attraction between the valence electrons of one atom and the nucleus of another http://education.jlab.org/frost/electroscope.html Episode 501

  2. Ionic Bond • Forms when valence electrons are transferred from one atom to another • Cation • Atom loses electrons to become (+) charged • Anion • Atom gains electrons to become (-) charged • In ionic compounds the ions are arranged in a crystal lattice; strong forces hold the ions together. Episode 501

  3. Properties of Ionic compounds • High melting and boiling points • Hard – not easily crushed • Conduct electricity when melted or dissolved because the ions are free to move Episode 501

  4. Covalent Bond • Electrons are shared , forming molecules • Covalent compounds have weaker forces holding the molecules together • Properties of covalent compounds • Lower melting and boiling points • Many covalent compounds are volatile liquids or gases • Softer – easier to crush • Are not conductors of electricity Episode 501

  5. Electronegativity • Property that tells how strong an atom’s attraction is for electrons • Oxygen en. = 3.5 • Hydrogen en. = 2.1 • Since oxygen has a greaterelectronegativity than hydrogen, oxygen holds onto the electrons stronger, giving oxygen a partial negative charge and the hydrogen a partial positive charge. Episode 501

  6. Polar covalent bond • Electrons are shared unequally creating partially charged ends or poles • Nonpolar covalent bonds • Electrons are shared equally because the atoms have the same or nearly the same electronegativities Ionic Bond Polar Covalent Bond Nonpolar Covalent Bond Episode 501

  7. Examples: • Mg and F? • Mg en.= 1.2 • F en.= 4.0 • 4.0 – 1.2 = 2.8 • Ionic • S and Cl? • S en.= 2.5 • Cl en.= 3.0 • 3.0 – 2.5 = 0.5 • Polar covalent • Problem Set #1 • Li and Cl? • C and O? • Na and Cl? • Cl and Br? • S and H? Episode 501

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