Metallic & Polar Covalent Bonds Describe how metals bond and form alloys Describe the way different molecules bond to each other

Metallic Bonds and Properties Metallic bonds form between metal elements The valence electrons of metal atoms can be modeled as a sea of electrons The electrons are mobile and can drift from one part of the metal to another This is how electricity works

Crystalline Structure of Metals Metal atoms are arranged in very compact and orderly patterns There are three basic patterns

Alloys The properties of alloys are often better than those of their component elements Examples: Sterling silver (silver and copper) is more durable than pure silver Steels (iron, carbon, boron, chromium etc) resist corrosion, have better ductility, hardness, and toughness

Molecular Orbitals Sigma bonds form when 2 atomic orbitals combine, forming a symmetrical orbital around an axis Pi bonds form when p orbitals overlap end-to-end forming sausage-shaped regions above and below the bond axis

VSEPR Theory Valence Shell Electron-Pair Repulsion Repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible

Bond Polarity Nonpolar covalent bonds form when bonding electrons are shared equally Diatomic molecules are nonpolar Polar covalent bond, or a polar bond, is a bond between atoms in which the electrons are shared unequally The more electronegative atom attracts electrons and gains a slight negative charge, the less electronegative atom gains a slightly positive charge. Example: Water

Attractions Between Molecules Van der Waals Forces consist of dipole interactions and dispersion forces Weakest attractions between molecules Dipole interactions occur when polar molecules are attracted to one another Dispersion forces occur when moving electrons in a nonpolar molecule are momentarily more on one side than other. Momentary dipole

Hydrogen Bonds Attractive forces in which a hydrogen which is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom.

Network Solid A solid in which all of the atoms are covalently bonded to each other Examples: Diamond and Silicon carbide

Ionic vs Covalent Lab Hypothesis (in lab Notebook) What properties of a compound will you use to determine if a bond is ionic or covalent? Choose three properties be sure to include why these properties will be useful in determining the bond type. You will be writing a conclusion for the ionic vs covalent lab. You will be asked to provide multiple pieces of evidence for why you labeled a compound ionic or covalent. You will also be asked to include an evaluation of your hypothesis. Was your initial plan to test specific properties of a compound in support of your findings?