Chemical BONDING

Chemical Bond A chemical bond results as atoms try to achieve a stable octet (or duet) in their outer shell just like the noble gases

Two Major Types of Bonding SALTS Crystals Ionic Bonding forms ionic compounds transfer of e- between valence shells Covalent Bonding forms molecules sharing e- between valence shells

One other type of bonding Metallic bonding Occurs between atoms of a metal or MIXTURE OF METALS (alloys) Ex. Al: aluminum foil Ex. Cu: copper wire Ex. Steel Valence e- are mobile (move freely among all metal atoms) Metallic characteristics High m.p. temps, ductile, malleable, shiny Good conductors of heat and electricity

Positive ions (nuclei) in a sea of electrons

[METAL ]+ [NON-METAL ]- Ionic Bonds form between [METAL ]+ [NON-METAL ]- Lost e- Gains e-

also . . . The bond to a POLYATOMIC ION ex. KNO3 ex. NH4Cl

Pairs of e- are shared between non-metal atoms Covalent Bonding Pairs of e- are shared between non-metal atoms H2O NO3- NaCl

In covalent bonding Electrons can be shared equally which makes the bond NON-POLAR

Or Electrons can be shared Unequally which makes the bond POLAR

What determines the polarity of the bond? Electronegativity What is Electronegativity? How strong an atom pulls on electrons of other atoms…….

Properties of Ionic Compounds

Form crystal lattice structures because of alternating anions(-) and cations (+)

Hard, angular crystals at room temp ~20oC

high melting point temperatures ex. NaCl 801oC (1,474oF) Remember H2O melts at 0oC!

nonconductors of electricity in solid phase good conductors in liquid phase or dissolved in water (aq) Salts & Solution PhET

Properties of Molecular Substances Covalent bonding Low m.p. temp and b.p. temps relatively soft solids as compared to ionic compounds NONconductors of electricity in any phase

The End