Ch400Ch7LN1 - Covalent Bonds and Molecular Structure What...

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What is Chemical Bonding? • A chemical bond is a strong attraction or force which holds atoms or ions together in a chemical compound. Why do Atoms Form Chemical Bonds? • Remember the Octet Rule: atoms tend to gain, lose, or share electrons in order to have 8 valence electrons or a full energy level. • The valence electrons are the electrons which are involved in chemical bonds. • By reacting to form chemical bonds, many atoms fulfill the octet rule. And they form more stable compounds! Chemical Bonding: Ionic vs. Covalent • Ionic Bonding: a chemical bond formed between a cation and an anion (or a metal and a nonmetal) • You learned that metals tend to lose electrons, while nonmetals tend to gain electrons. • So metals tend to transfer electrons to nonmetals. • Ionic bonding occurs when electrons are transferred from the metal to the nonmetal. M + X --> M + + X - or M + X --> MX • The strong attraction of a positive charge to a negative charge holds them together in an ionic bond. • Because ionic bonds are very strong, ionic compounds are solids at room temperature. • Ionic compounds tend to have VERY high melting and boiling points and high lattice energies. • Remember, lattice energies are thousands of kJ/mol so it takes a lot of energy to break apart an ionic crystal. Na F + + Na + F - e - Covalent Bonds and Molecular Structure Covalent Bonding and Covalent Compounds: A bond where atoms share electrons. • Remember that it is difficult for atoms to gain or lose 3 or more electrons. • So many atoms share electrons in order to “have” 8 valence electrons. • It’s like sharing a room with someone, it’s both “your” room, but you’re sharing. • Wnen atoms share one or more electrons, a covalent bond is formed because both nuclei are attracted to the shared electrons. Compounds which contain covalent bonds are called covalent compounds or molecular compounds or molecules.
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Covalent Bonding Continued • The two atoms share one or more electrons; with the shared electrons having a high probability of being found between the two nuclei. • The above figure represents the hydrogen molecule, where 2 electrons are shared equally between the two atoms. • The 7 diatomic elemental molecules share electrons equally just as the above figure shows.
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This note was uploaded on 06/25/2008 for the course CHEM 400-401 taught by Professor Dr.samples during the Fall '06 term at American River.

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Ch400Ch7LN1 - Covalent Bonds and Molecular Structure What...

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