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Prepared by PhD Halina Falfushynska

Prepared by PhD Halina Falfushynska. Lecture III. Chemical Bonds. Valence bond theory. Bonds occur due the sharing of electrons between atoms; The attraction of bonding electrons to the nuclei of the bonded atoms leads to lower energy, and therefore the formation of a bond;

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Prepared by PhD Halina Falfushynska

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  1. Prepared by PhD Halina Falfushynska Lecture III. Chemical Bonds

  2. Valence bond theory • Bonds occur due the sharing of electrons between atoms; • The attraction of bonding electrons to the nuclei of the bonded atoms leads to lower energy, and therefore the formation of a bond; • Two types of bonds can form (sigma and pi).

  3. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons Gain 4 electrons • C would like to • N would like to • O would like to Gain 3 electrons Gain 2 electrons

  4. Covalent Bond • Between nonmetallic elements of similar electronegativity. • Formed by sharing electron pairs • Stable non-ionizing particles, they are not conductors at any state • Examples; O2, CO2, C2H6, H2O, SiC

  5. Covalent Bonds

  6. NONPOLAR COVALENT BONDS - when electrons are shared equally (H2 or Cl2) POLAR COVALENT BONDS - when electrons are shared but shared unequally (HF, HCl)

  7. The covalent bond in H2

  8. The covalent bond in F2

  9. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

  10. Polar Covalent Bonds: Unevenly matched, but willing to share.

  11. The covalent bond in HF

  12. Formation of Ions from Metals • Ionic compounds result when metals react with nonmetals • Metals loseelectrons to match the number of valence electrons of their nearest noble gas • Positive ionsform when the number of electrons are less than the number of protons Group 1 metals ion 1+ Group 2 metals ion 2+ • Group 13 metals ion 3+

  13. Ionic Bond • Between atoms of metals and nonmetals with very different electronegativity • Bond formed by transfer of electrons • Produce charged ions all states. Conductors and have high melting point. • Examples; NaCl, CaCl2, K2O

  14. Ionic Bonds: One Big Greedy Thief Dog!

  15. Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

  16. METALLIC BONDbond found in metals; holds metal atoms together very strongly

  17. Metallic Bond • Formed between atoms of metallic elements • Electron cloud around atoms • Good conductors at all states, lustrous, very high melting points • Examples; Na, Fe, Al, Au, Co

  18. Metallic Bonds: Mellow dogs with plenty of bones to go around.

  19. Ionic Bond, A Sea of Electrons

  20. Types of chemical bond

  21. Types of chemical bond

  22. BOND LENGTH AND STRENGTH

  23. BOND LENGTH AND STRENGTH

  24. Molecular Orbital Diagrams (H2)

  25. Molecular Orbital Diagrams (He2)

  26. Molecular orbital diagram for homonuclear diatomics

  27. Molecular orbital diagram for O2 Paramagnetic properties

  28. Molecular orbital diagram for nitrogen monoxide

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