Bond Types You will be able to identify the type of bond between atoms based upon their EN.

Bonding The type of bonds depend on the electronegativities of the elements involved EN: the attraction an atom for a shared pair of electrons (Strength) Two divisions of bonds Intramolecular Bonds within a molecule Intermolecular Bonds between multiple molecules H Cl

Intramolecular Bonds Ionic Bonds (usually M-NM) Electrons are transferred + and – ions attract each other and form a crystalline structure Dissociate in water Conduct electricity Covalent Bonds (usually all NM) Electrons are shared by having orbitals overlap Nonconductors Polar Covalent Bonds Electrons are still shared but NOT equally Na-Cl Cl-Cl H-Cl

Polar Covalent Bonds Because of the unequal sharing of electrons, polar covalent molecules attract other molecules Similar to ionic bond attraction CovalentPolar covalentIonic Difference in electronegativity

Examples EN table p.169 H-O H-Br Cl-Cl Na-F EN diffBond type%Ionic

Intermolecular Bonds Hydrogen Bonds Hydrogen is attracted to and bonds to N, O or F from another molecule in a polar covalent molecule O HH HH H H O O

Van der Waal Forces Dipole-Dipole (dispersion forces) Similar to H-bonds but can exist with other atoms London Forces Momentary dipoles in NONPOLAR molecules H Cl He

Strength of Forces I > C/PC > H-bonds > dipole-dipole > london forces Melting point, boiling increases

Metallic Bonds

Ex: Cu – Au – Ag – Fe “sea” of valence electrons responsible for luster (shiny) conductors (e - move heat and electricity) electron sea model  delocalized e - e - are free to move

Alloys: metallic mixtures Brass Cu & Zn Bronze Cu, Zn, & Sn 10 ct. gold Au, Ag, & Cu Stainless Steel Fe, Cr, & Ni Sterling Silver Ag, Cu