Chpt_09_LE_Part%20A

Chpt_09_LE_Part%20A - Chemical Bonding I: Lewis Theory...

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1 Chemical Bonding I: Chemical Bonding I: Lewis Theory Lewis Theory Chapter 9 Chapter 9 – Part A Part A Types of Bonds electrons pooled Metallic metal to metal electrons shared Covalent nonmetals to nonmetals electrons transferred Ionic metals to nonmetals Bond Characteristic Type of Bond Types of Atoms Chemical bonds forms because they lower the potential energy between the charged particles. The energy of interaction between charged particles is given as (q 1 q 2 /r).
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2 Lewis Electron Dot Model Lewis Electron Dot Model ± Quantum mechanics is the key to understand the electronic structure of atom ± However, Lewis electron dot model is a simplified qualitative way to understand the properties. Electrons that are held close to the nucleus. They are not involved in chemical bonds Electrons in atom Electrons that occupy outer regions of atom and take part in bonds Core electrons Valence electrons ± The number of valence electrons of a neutral atom in the main group elements = group number 1A 2A 3A 4A 5A 6A 7A 8A Li Be B C N O F Ne 1 e 2 e 3 e 4 e 5 e 6 e 7 e 8 e General Properties ± The maximum number of valence electrons is 8 (or 2 for first row elements) ± According to quantum mechanics, electrons in an atom are arranged in shells. The first shell can only accommodate 2 electrons. The second shell can accommodate a maximum of 8 electrons. ± First row elements ( H and He ) have valence electrons in the first shell. Their stability comes when the first shell is full (that is when the atom has 2 electrons). Thus, hydrogen atom can accept one electron to achieve stability. Helium atom already has 2 electrons, so it is stable and doesn’t react. ± Second row elements ( Li, Be, C, N, O and F ) have valence electrons in the second shell and core electrons in the first shell. Their stability comes when an atom either loses electrons so that the second shell becomes completely empty or gains electrons so that the second shell becomes completely full. The former situation applies to Li and Be while the later situation applies to C, N, O and F.
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3 Lewis Electron Dot Model Lewis Electron Dot Model ± Use symbol of element to represent nucleus and core electrons ± Valence electrons are represented by dots ± First four valence electrons are shown as dots on four sides of the atom.
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Chpt_09_LE_Part%20A - Chemical Bonding I: Lewis Theory...

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