15 Covalent Bonds & Lewis Structures

15 Covalent Bonds & Lewis Structures - Question...

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1 1 Question from last time: Why don’t carbon and oxygen form an ionic bond? Energy change = ionize C – attach e to O – stabilize ion pair = (1086 – 141 – 935) kJ/mol = +10 kJ/mol How many of the following statements are correct. The energy increases: C & O atoms are more stable than the C + O - pair C ionization energy is too large The O electron affinity is too small. Electronegativity difference is too small. A) 0 B) 1 C) 2 D) 3 E) 4 2 Do you agree or disagree with the following statement? A) agree B) disagree Configuration of Be (1s 2 2s 2 ) and Be - (1s 2 2s 2 2p) The electron affinity of Be is zero or small because the additional electron is in a 2p-orbital and is strongly repelled by the 1s and 2s electrons and thereby shielded from the attractive +4 nuclear charge. Question from Last Time
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2 3 Configuration of N (1s 2 2s 2 2p 3 ) and N - (1s 2 2s 2 2p 4 ) The electron affinity of N is zero because the additional electron is in a 2p-orbital and is strongly repelled by the other electrons in the 2p orbitals and thereby shielded from the attractive +7 nuclear charge. Question from Last Time Do you agree or disagree with the following statement? A) agree B) disagree 4 The Mysteries of Chemical Bonding Just 4 elements (C, H, N, and O) and occasionally a few others, produce millions of compounds with diverse properties forming the basis of life proteins, nucleic acids, enzymes and contributing to the quality of life. plastics, medicines, textiles The key to these diverse properties is the way the atoms are connected together – the chemical bonding! Testosterone C 19 HO 28 O 2
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3 5 Formation of Molecules Atoms combine to form molecules because the molecules have a lower energy than the separated atoms. Lower energy means the molecules are more stable. The attractive force that holds two atoms together in a molecule is called a bond. 6 Types of Bonds Ionic bond – one or more electrons are transferred from one atom to another. The ions are held together by the Coulomb force between opposite charges. Covalent bond – atoms share one or more pairs of electrons that have a high electron density between the two nuclei. The resulting Coulomb force between opposite charges holds the atoms together .
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This note was uploaded on 10/16/2009 for the course CHE 129/130 taught by Professor Hanson during the Fall '09 term at SUNY Stony Brook.

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15 Covalent Bonds & Lewis Structures - Question...

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