Fig 8.17 Periodic Table of the Elements

Fig 8.18Show only valence electrons!Electron dot notation for the representative elements

CHEMICAL BONDSCHAP 9

Homework for Chap 9

Read p 229 - 246Applying the Concepts: 1 13, 16 35, 38 44, 47 - 5

Compounds and Chemical ChangeElements are composed of extremely small particles called atoms.

Compounds are composed of atoms of more than one element held together by chemical bonds.

3. Molecule smallest particle of a compound that canexist and still retain characteristic chemical properties

Compounds occur as solids, liquids, and gases

Fig. 9.2 Common gases exist as atoms or molecules

Fig. 9.3Example of achemical reactionBurning magnesium (Mg)in airto produce magnesium oxide (milk of magnesia)Energy is released

Fig. 9.4 (A) Photosynthesis stores solar energyFig. 9.4 (B) Combustion releases solar energyReactantsProducts

Fig 8.20 Electron dot notation for representativeelements15678342Valence electrons outermost electrons in an atomOctet rule atoms attempt to acquire 8 valence electrons

Fig. 9.5

energy + Na Na+ + e

energy + Ca

energy + Al 56783412Ca2+ + eAl3+ + eFig 8.21

Three Types of Chemical Bonds Ionic bonds

Electrons are transferred from one atom to anotherOccur between a metal atom and a nonmetal atom

(2) Covalent bonds

Electrons are shared between two atomsOccur between two nonmetal atoms

Metallic bonds

Metal atoms share many electrons in a sea that is free to move throughout the metal

Formation of an ionic bond+ eNet reaction: Na + Cl Na+Cl + energyThis energy is called the heat of formation

Fig. 9.6 Model of the sodium chloride crystal+No molecules in an ionic compound!Na+ ionsCl ionsFormula unit

Fig. 9.7 The cubic crystal structure of sodium chloride

Ionic compounds consist of a combination of positive ions and negative ions Ions are formed as nonmetal atoms gain and metal atoms lose electrons to achieve stable noble gas structure The sum of the charges on the positive ions and negative ions in each formula unit must equal zero How do we determine the formula for an ionic compound?

Formula of Ionic CompoundsAl2O3Al3+O2-CaBr2Ca2+Br-Al and OCa and Br

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