Chemical Bonding

Two main types of bonds: o Ionic bonding results from attractions among ions, which are formed by the transfer of one or more electrons from one atom to another. o Covalent bonding results from sharing one or more electrons between two atoms. o Ionic bonding results from attractions among ions, which are formed by the transfer of one or more electrons from one atom to another. o Covalent bonding results from sharing one or more electrons between two atoms.

Ionic Bonding Formation of Ionic Compounds  An ion is an atom or a group of atoms possessing a net electrical charge.  Ions come in two basic types: positive (+) ions negative (-) ions  Metals react with Non-metals  (+) ions bind to (-) ions Formation of Ionic Compounds  An ion is an atom or a group of atoms possessing a net electrical charge.  Ions come in two basic types: positive (+) ions negative (-) ions  Metals react with Non-metals  (+) ions bind to (-) ions

 Ionic compounds form 3-D crystal lattices of oppositely charged ions.  Ionic compounds have high melting points as the attraction between (+) and (-) ions are strong  Ionic compounds form 3-D crystal lattices of oppositely charged ions.  Ionic compounds have high melting points as the attraction between (+) and (-) ions are strong

Why are ionic solids brittle? Strong repulsive forces between similarly charged ions

What is this strong ionic solid?

Electrostatic attraction holds the oppositely charged ions together No such thing as separate molecules of NaCl

Ionic solids are soluble FCharged ions are highly attractive to water FWater will completely surround the ion and dissociate it from the lattice until it dissolves completely FDissociation of saltDissociation of salt FCharged ions are highly attractive to water FWater will completely surround the ion and dissociate it from the lattice until it dissolves completely FDissociation of saltDissociation of salt

Atoms try to attain noble-gas electronic configurations Li  Li + Ca  Ca 2+ Al  Al 3+

C  C 4- P  P 3- O  O 2- Br  Br -

Writing Formulas

aluminium Metals like aluminium, needs to give away 3 electrons to a non-metal to become stable MetalNon-metal

Aluminumchlorine Al +3 Steps for Writing Formulas: eg. Aluminum and chlorine 1. Write the symbol and oxidation number (ion charge) for aluminum Al +3

Cl Write the symbol and oxidation number for Chlorine Cl -1

Al +3 Cl Criss-cross the oxidation numbers for each atom Al +3 Cl -1

AlCl 3 4. Write the formula with subscripts and no charges AlCl 3 Note: - metals always go first - no need to show “1’s”

What does the formula tell us? one aluminum three chlorine That one aluminum atom requires three chlorine atoms to become a stable ionic compound

Drawing Electron-Dot Structures

Molecular Compounds

Electrons are shared among atoms; molecule is electrically neutral

Atoms WITHIN the molecule are held together by strong covalent bonds, an intramolecular force. Each molecule is slightly attracted to each other by weak intermolecular forces which are easily overcome by heating a substance.

Intramolecular force Intermolecular force