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This chapter discusses the different types of chemical bonds, including ionic, covalent, metallic, and hydrogen bonds. It explains the concepts of electronegativity, Lewis structures, and the octet rule. The text also covers the characteristics and properties of each bond type.
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Chapter 7 • Chemical Bonds
Chemical bond • Link between atoms that results from attractions of their nuclei for e-
1. Ionic bond • Attraction between (+) and (-) ions, exchange of e- • Usually between metals and nonmetals
Ion • Atom or group of atoms with a (+) or (-) charge • Cation: (+) chg • Anion: (-) chg
Polyatomic ions • Charged group of bonded atoms • e.g. phosphate ion (PO43-)
2. Covalent bonds • Sharing of e- • Usually between nonmetals
Covalent bonding • Molecule- smallest unit quantity of matter that can exist by itself, e.g. atom of He, O2, H2O • Diatomic molecule-2 atoms, e.g. HCl, H2
Chemical bonds are usually not completely ionic or covalent Difference in electronegativity 4.0 1.7 0.3 0.0 Polar covalent Non polar covalent ionic
electronegativity • Measure of ability of an atom in a chem. cmpd. to attract electrons
Chemical formula • Type and relative # of atoms in a chemical compound, e.g. H2O
Octet rule • Atoms often gain, lose, or share electrons to achieve the same number of electrons as the noble gas closest to them in the periodic table • Because all noble gasses (except He) have filled s and p valence orbitals (8 electrons), many atoms undergoing reactions also end up with 8 valence electrons. • Octet Rule: Atoms tend to lose, gain, or share electrons until they are surrounded by 8 valence electrons • Note: there are exceptions to the octet rule, e.g.He
Valence electrons • Electrons lost, gained, or shared in formation of chemical cmpds.
Lewis structures • N2 (nitrogen) • Carbon tetrachloride
Lewis structure • Structural formula
Structural formula • Indicates the kind, number, arrangement, and bonds of atoms in molecules
Single bonds • Sharing (1) pr. of e-
Double bond • Sharing (2) pr. of e-
Triple bond • Sharing (3) pr of e-
3. Metallic bonds • Metal-metal bonds, electron ‘sea’
Metallic bonding • Results from attraction between (+) ions and surrounding mobile electrons (electron sea) • Motion of free electrons accounts for high conductivity of heat and electricity • Malleability and ducticity possible because bonding is not directional
4. Hydrogen bonds • Weak bonds between molecules due to partial charges on atoms • e.g. water
Review: ionic or covalent? • Ca and Cl • Ionic • Na and F • Ionic • N and O • Covalent • H and H • Covalent
Review: Lewis Structure • H + H + O • C2H4 (ethene)
Define: • Covalent bond • Ionic bond • Metallic bond • Hydrogen bond • Diatomic molecule • Cation • Anion • Electronegativity