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Bond Energy Activity

Bond Energy Activity. Using the table of bond energies (table 1), calculate the heat of reaction (  H) for the formation of the diatomic molecules in the (table 2) We will divide up the table amongst groups. Show calculation work in notebooks. Electronegativity.

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Bond Energy Activity

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  1. Bond Energy Activity • Using the table of bond energies (table 1), calculate the heat of reaction (H) for the formation of the diatomic molecules in the (table 2) • We will divide up the table amongst groups. • Show calculation work in notebooks.

  2. Electronegativity • As the bond energy shows, Pauling found that HCl has a greater bond energy (431 kJ) than the average of the H2 and Cl2 bonds (339.5 kJ) • He attributed this extra strength to partial ionic character, which lowered the chemical energy of the molecule.

  3. Electronegativity • Using these bond strength concepts, Pauling assigned arbitrary values of “electronegativity” • Electronegativity: the ability of an atom to attract electrons in a covalent bond to itself. • What do these trends remind you of ?

  4. Trends in Electronegativity

  5. Trends in Electronegativity • Now try page 2 of activity

  6. Electronegativity and Bond Polarity • In molecules, differences in electronegativity allows us to describe the “sharing” of electrons between atoms. • Does the average location of the shared electron pair have to be half-way between the atoms?

  7. Polarity of Covalent Bonds • Unequal sharing of electrons in a bond leads to the development of partial charges separated from one another - this phenomenon is called polarity. • The greater the charge separation, the more like an ionic bond the covalent bond becomes. We speak of the relative ionic and covalent character of the bond.

  8. Bonds can be found with a range of polarities, from completely ionic to completely covalent. When will a bond be polar?Figure 7.10 Bonds: Ionic, Polar Covalent, Non-Polar Covalent

  9. Electronegativity and Bond Type • Differences in electronegativity also allow us to approximate whether atoms will transfer or share electrons when forming a bond.

  10. Practice: Polarity and Electronegativity • What is the relative polarity of the bonds in the following sets?F2, HFFCl, Cl2OF, MgOOH, CH, HH, HF Electronegativities F 4.0 O 3.5 Cl 3.0 C 2.5 H 2.1 B 2.0 Mg 1.2

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