Ionic, Metallic, & Polar Covalent Bonds Describe how metals bond and form alloys Describe how Atoms 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

Alloys A combination of metals or a metal and another element. Often done to increase material strength or to help resist corrosion 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

Formation of Ionic Compounds Ionic compounds form when a metal transfers one or more electrons to a nonmetal. Ionic compounds are two or more elements held together by opposite charge attraction. Ionic compounds are composed of cations and anions, usually a metal cation and nonmetal anion. Are electrically neutral The Difference in electronegativity of ionic bonded atoms is greater than 2

Bond Character Example-Fluorine Atoms: NaCl Electron Movement: Electronegativity Difference: 3.16-.93=_____ Bond Type:

Properties of Ionic Compounds Crystalline Solids (at room temp) High Melting Point Conduct an electric current when melted or dissolved in water Made up of a metal and non metal Generally a brittle solid Most ionic compounds are crystalline solids at room temperature They have a regular repeating 3-D patterns Ionic compounds generally have high melting points

Covalent Compounds Formation Properties Covalent compounds are formed when two or more nonmetals share electrons. Generally insoluble in water Non conductive Can be solid, liquid, or gas Made up of non metals

Bond Polarity Nonpolar covalent bonds form when bonding electrons are shared equally Diatomic molecules are nonpolar Difference in electronegativity of bonded atoms is between 0 & .4 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. Difference in electronegativity of bonded atoms is between .4 & 2 Example: Water

Bond Character Example-Fluorine Molecule: F2 Electron Movement: Electronegativity Difference: 4.0-4.0=_____ Bond Type:

Bond Character Example-Fluorine Molecule: H2O Electron Movement: Electronegativity Difference: 3.44-2.2=_____ Bond Type:

Molecule Shapes Molecular Geometry: The arrangement of atoms within a given molecule. VSEPR: Valence Shell Electron Pair Repulsion Is based on simple electrostatic repulsions of electron pairs Assumption: Electrons in chemical bonds( single, double, or triple) and unshared electron pairs are negative centers that repel each other

VSEPR Shapes Shape Atoms Bonded Electron Regions Example Linear 2 Bent 3 or 4 Trigonal Planar 3 Trigonal Pyramidal 4 Tetrahedral

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

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

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