Chapter 7 Chemical Bonds Chemical bond Link between atoms that results from attractions of their nuclei for e -
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Chapter 7Chapter 7
Chemical BondsChemical Bonds
Chemical bondChemical bond
Link between atoms Link between atoms that results from that results from attractions of their attractions of their nuclei for enuclei for e--
1. Ionic bond1. Ionic bond
Attraction between (+) and (-) ions, Attraction between (+) and (-) ions, exchange of eexchange of e- -
Usually between metals and nonmetalsUsually between metals and nonmetals
IonIon
Atom or group of atoms with a (+) or (-) Atom or group of atoms with a (+) or (-) chargecharge
Cation: (+) chgCation: (+) chg Anion: (-) chgAnion: (-) chg
e.g. sodiume.g. sodium
e.g. chlorinee.g. chlorine
Na and Cl ions Na and Cl ions ionic bond ionic bond
Polyatomic ionsPolyatomic ions
Charged group of bonded atomsCharged group of bonded atoms e.g. phosphate ion e.g. phosphate ion (PO(PO44
3-3-))
2. Covalent bonds2. Covalent bonds
Sharing of eSharing of e--
Usually betweenUsually between
nonmetals nonmetals
Covalent bondingCovalent bonding
Molecule- smallest unit quantity of matter Molecule- smallest unit quantity of matter that can exist by itself, e.g. atom of He, that can exist by itself, e.g. atom of He, OO22, H, H22OO
Diatomic molecule-2 atoms, e.g. HCl, HDiatomic molecule-2 atoms, e.g. HCl, H22
e.g. hydrogen moleculee.g. hydrogen molecule
Bond typesBond types
Chemical bonds are usually not Chemical bonds are usually not completely ionic completely ionic oror covalent covalent
4.0 1.7 0.3 0.0
ionicPolar covalent
Non polar covalent
Difference in electronegativity
electronegativityelectronegativity
Measure of ability of an atom in a chem. Measure of ability of an atom in a chem. cmpd. to attract electronscmpd. to attract electrons
Chemical formulaChemical formula
Type and relative # of atoms in a Type and relative # of atoms in a chemical compound, e.g. Hchemical compound, e.g. H22OO
ee-- config. config.andandbondingbonding
Octet ruleOctet rule
Atoms often gain, lose, or share electrons to Atoms often gain, lose, or share electrons to achieve the same number of electrons as the noble achieve the same number of electrons as the noble gas closest to them in the periodic tablegas closest to them in the periodic table
Because all noble gasses (except He) have filled Because all noble gasses (except He) have filled ss and and pp valence orbitals (8 electrons), many atoms valence orbitals (8 electrons), many atoms undergoing reactions also end up with 8 valence undergoing reactions also end up with 8 valence electrons. electrons.
Octet RuleOctet Rule: : Atoms tend to lose, gain, or share Atoms tend to lose, gain, or share electrons until they are surrounded by 8 valence electrons until they are surrounded by 8 valence electronselectrons
Note: there are exceptions to the octet rule, e.g.He Note: there are exceptions to the octet rule, e.g.He
Valence electronsValence electrons
Electrons lost, gained, or shared in Electrons lost, gained, or shared in formation of chemical cmpds.formation of chemical cmpds.
Lewis structuresLewis structures
NN2 2 (nitrogen)(nitrogen)
Carbon tetrachlorideCarbon tetrachloride
Lewis structureLewis structure
Structural formulaStructural formula
Structural formulaStructural formula
Indicates the kind, number, arrangement, Indicates the kind, number, arrangement, and bonds of atoms in moleculesand bonds of atoms in molecules
Single bondsSingle bonds
Sharing (1) pr. of eSharing (1) pr. of e--
Double bondDouble bond
Sharing (2) pr. of eSharing (2) pr. of e--
Triple bondTriple bond
Sharing (3) pr of eSharing (3) pr of e--
3. Metallic bonds3. Metallic bonds
Metal-metal bonds, electron ‘sea’Metal-metal bonds, electron ‘sea’
Metallic bondingMetallic bonding
Results from attraction between (+) ions Results from attraction between (+) ions and surrounding mobile electrons and surrounding mobile electrons (electron sea)(electron sea)
Motion of free electrons accounts for Motion of free electrons accounts for high high conductivity of heat and electricityconductivity of heat and electricity
Malleability and ducticity possible Malleability and ducticity possible because bonding is not directionalbecause bonding is not directional
4. Hydrogen bonds4. Hydrogen bonds
Weak bonds Weak bonds betweenbetween molecules due to molecules due to partialpartial charges on atoms charges on atoms
e.g. watere.g. water
Polarity of water Polarity of water molecule molecule hydrogen hydrogen bondingbonding
Review: ionic or Review: ionic or covalent?covalent?
Ca and ClCa and Cl IonicIonic Na and FNa and F IonicIonic N and ON and O CovalentCovalent H and HH and H CovalentCovalent
Review: Lewis StructureReview: Lewis Structure
1.1. H + H + OH + H + O
2.2. CC22HH4 4 (ethene)(ethene)
What kind of bondWhat kind of bondss??
Define:Define:
Covalent bondCovalent bond Ionic bondIonic bond Metallic bondMetallic bond Hydrogen bondHydrogen bond Diatomic moleculeDiatomic molecule CationCation AnionAnion ElectronegativityElectronegativity
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