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Bond Energies

Bond Energies. Types of Chemical Bonds Chapter 8. Bond Energy. The strength of the interaction between atoms can be measured by the amount of energy it takes to break that bond. Ionic Bonds. Atoms form ions. Ions are attracted to oppositely charged ions.

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Bond Energies

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  1. Bond Energies Types of Chemical Bonds Chapter 8

  2. Bond Energy • The strength of the interaction between atoms can be measured by the amount of energy it takes to break that bond.

  3. Ionic Bonds • Atoms form ions. • Ions are attracted to oppositely charged ions. • Cations and anions form ionic compounds

  4. Ionic Bonding • Metals and non metals form ionic bonds. • The degree of ionic bonding depends on the nature of the elements in the compound. • Ionic compounds are often called salts.

  5. Coulomb’s Law • The energy of an interaction between a pair of ions can be calculated. • k= 2.31 x 10-19 Jnm

  6. Why do ions form? • The ion pair in a compound has lower energy that the separated ions. • What is the energy of NaCl when the distance between the nuclei is 2.76 A or 0.276 nm?

  7. Answer: • E=(2.31 x 10-19 Jnm)[(+1)(-1)/(0.276 nm)2] • = -3.03 x 10-18 J • Coulomb’s Law may also be used to find the Energy of the repulsion between two like charged ions.

  8. Covalent Bonding • What about atoms with like charges? • When two H’s are brought together, they actually repulse. • Under what conditions will they bond?

  9. Covalent Bonds • When they are too close the repulsive force of the nuclei increases the energy. • When they are too far apart the energy is zero. • At the bond length, the energy is lowest and bonding occurs.

  10. Covalent bonding • When two or more elements share electrons. • When the electrons are shared equally, it is non polar covalent.

  11. Polar covalent bonding • When there is an unequal sharing of electron in a covalent bond. • Due to the relative electronegativity of the elements.

  12. Electronegativity

  13. Polar molecules • When there is an unequal sharing of electrons, partial charges form on the compound. • If that compound may align in an electric field, it is polar.

  14. Polar moleculesNot in magnetic field & in magnetic field

  15. What makes a molecule polar? • Unequal sharing of electrons is due to differences in electronegativity.

  16. Relative polarities • Order the following bonds according to their polarity. • H-H; O-H; Cl-H; S-H & F-H • Answer: • H-H < S-H < Cl-H < O-H< F-H • 2.1-2.1; 2.5-2.1, 3.0-2.1, 3.5-2.1, 4.0-2.1 • 0 0.4 0.9 1.4 1.9 • Covalent  Polar Covalent Bond

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