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Chem1- 4th Q 1st LT

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Rio Ca単al
Rio Ca単al

1) Valence electrons participate in chemical bonding and their configuration determines an element's reactivity. 2) In 1916-1919, Lewis and Langmuir proposed that atoms bond to acquire stable noble gas configurations. 3) Ionic bonds form when electrons are transferred between atoms. Covalent bonds form when electron pairs are shared between atoms.

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Chem1- 4th Q 1st LT
Chemical Bonding I: Basic Concepts
Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that particpate in chemical bonding. Group e- configuration # of valence e- 1A ns1 1 2A ns2 2 3A ns2np1 3 4A ns2np2 4 5A ns2np3 5 6A ns2np4 6 7A ns2np5 7 9.1
In the period 1916-1919, two Americans, G.N. Lewis and Irving Langmuir, and a German, Walther Kossel, advanced an important proposal about chemical bonding: Something unique in the electron configurations of noble gas atoms accounts for their inertness, and atoms of other elements combine with one another to acquire electron configurations like noble gas atoms. Some fundamental ideas of Lewis theory Electrons, especially those of the outermost (valence) electronic shell, play a fundamental role in chemical bonding. In some cased electrons are transferred from one atom to another. Positive and negative ions are formed and attract each other through electrostatic forces called ionic bonds. In other cases one or more pairs of electrons are shared between atoms, this sharing of electrons is called covalent bond. Electrons are transferred, or shared, in such a way that each atom acquires an especially stable electron configuration. Usually this is a noble gas configuration, one with eight outer shell electrons, or an octet.
Lewis symbol consists of a chemical symbol to represent the nucleus and core (inner shell) electrons of an atom, together with dots placed around the symbol to represent the valence (outer shell) electrons. Write the Lewis symbol of the following elements 1. Si 2. N 3. P 4. As 5. Sb 6. Bi 7. Al 8. Al 9. Al 10. I 11. Se 12. Ar Write the Lewis symbol of the following 1. Sn 2. Br 3. Na+ 4. S2-
Lewis structure is a combination of Lewis symbols that represents either the transfer or sharing of electrons in a chemical bond. Write Lewis structures for the following compounds (a) BaO (b) MgCl2 (c) Al2O3 (d) Na2S (e) Mg3N2 (f) calcium iodide (g)barium sulfide (h) lithium oxide
9.1
The Ionic Bond Li + F Li+ F - 1s22s1 1s22s22p5 [He] [Ne] 2p6 1s21s22s2 Li Li+ + e - - e + F F - Li+ + F - Li+ F - 9.2
A covalent bond is a chemical bond in which two or more electrons are shared by two atoms. Why should two atoms share electrons? F + F F F 7e- 7e- 8e- 8e- Lewis structure of F2 lone pairs F F lone pairs single covalent bond single covalent bond lone pairs F F lone pairs 9.4
Lewis structure of water single covalent bonds H + O + H H O H or H O H 2e- 8e- 2e- Double bond two atoms share two pairs of electrons O C O or O C O - 8e 8e 8e double bonds - - double bonds Triple bond two atoms share three pairs of electrons N N or N N - 8e 8e - triple bond triple bond 9.4
Lengths of Covalent Bonds Bond Bond Length Type (pm) C-C 154 CC 133 CC 120 C-N 143 CN 138 CN 116 Bond Lengths Triple bond < Double Bond < Single Bond 9.4
9.4
Polar covalent bond or polar bond is a covalent bond with greater electron density around one of the two atoms electron rich electron poor region region e- poor e- rich H F H F d+ d- 9.5
Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond. Electron Affinity - measurable, Cl is highest X (g) + e- X-(g) Electronegativity - relative, F is highest 9.5
9.5
9.5
Classification of bonds by difference in electronegativity Difference Bond Type 0 Covalent 2 Ionic 0 < and <2 Polar Covalent Increasing difference in electronegativity Covalent Polar Covalent Ionic share e- partial transfer of e- transfer e- 9.5

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Chem1- 4th Q 1st LT

  • 2. Chemical Bonding I: Basic Concepts
  • 3. Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that particpate in chemical bonding. Group e- configuration # of valence e- 1A ns1 1 2A ns2 2 3A ns2np1 3 4A ns2np2 4 5A ns2np3 5 6A ns2np4 6 7A ns2np5 7 9.1
  • 4. In the period 1916-1919, two Americans, G.N. Lewis and Irving Langmuir, and a German, Walther Kossel, advanced an important proposal about chemical bonding: Something unique in the electron configurations of noble gas atoms accounts for their inertness, and atoms of other elements combine with one another to acquire electron configurations like noble gas atoms. Some fundamental ideas of Lewis theory Electrons, especially those of the outermost (valence) electronic shell, play a fundamental role in chemical bonding. In some cased electrons are transferred from one atom to another. Positive and negative ions are formed and attract each other through electrostatic forces called ionic bonds. In other cases one or more pairs of electrons are shared between atoms, this sharing of electrons is called covalent bond. Electrons are transferred, or shared, in such a way that each atom acquires an especially stable electron configuration. Usually this is a noble gas configuration, one with eight outer shell electrons, or an octet.
  • 5. Lewis symbol consists of a chemical symbol to represent the nucleus and core (inner shell) electrons of an atom, together with dots placed around the symbol to represent the valence (outer shell) electrons. Write the Lewis symbol of the following elements 1. Si 2. N 3. P 4. As 5. Sb 6. Bi 7. Al 8. Al 9. Al 10. I 11. Se 12. Ar Write the Lewis symbol of the following 1. Sn 2. Br 3. Na+ 4. S2-
  • 6. Lewis structure is a combination of Lewis symbols that represents either the transfer or sharing of electrons in a chemical bond. Write Lewis structures for the following compounds (a) BaO (b) MgCl2 (c) Al2O3 (d) Na2S (e) Mg3N2 (f) calcium iodide (g)barium sulfide (h) lithium oxide
  • 7. 9.1
  • 8. The Ionic Bond Li + F Li+ F - 1s22s1 1s22s22p5 [He] [Ne] 2p6 1s21s22s2 Li Li+ + e - - e + F F - Li+ + F - Li+ F - 9.2
  • 9. A covalent bond is a chemical bond in which two or more electrons are shared by two atoms. Why should two atoms share electrons? F + F F F 7e- 7e- 8e- 8e- Lewis structure of F2 lone pairs F F lone pairs single covalent bond single covalent bond lone pairs F F lone pairs 9.4
  • 10. Lewis structure of water single covalent bonds H + O + H H O H or H O H 2e- 8e- 2e- Double bond two atoms share two pairs of electrons O C O or O C O - 8e 8e 8e double bonds - - double bonds Triple bond two atoms share three pairs of electrons N N or N N - 8e 8e - triple bond triple bond 9.4
  • 11. Lengths of Covalent Bonds Bond Bond Length Type (pm) C-C 154 CC 133 CC 120 C-N 143 CN 138 CN 116 Bond Lengths Triple bond < Double Bond < Single Bond 9.4
  • 12. 9.4
  • 13. Polar covalent bond or polar bond is a covalent bond with greater electron density around one of the two atoms electron rich electron poor region region e- poor e- rich H F H F d+ d- 9.5
  • 14. Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond. Electron Affinity - measurable, Cl is highest X (g) + e- X-(g) Electronegativity - relative, F is highest 9.5
  • 15. 9.5
  • 16. 9.5
  • 17. Classification of bonds by difference in electronegativity Difference Bond Type 0 Covalent 2 Ionic 0 < and <2 Polar Covalent Increasing difference in electronegativity Covalent Polar Covalent Ionic share e- partial transfer of e- transfer e- 9.5