Chemical BONDING

Chemical Bond A bond results from the attraction of nuclei for electrons All atoms trying to achieve a stable octet IN OTHER WORDS the p+ in one nucleus are attracted to the e- of another atom Electronegativity

What did the atom of fluorine say to the atom of sodium? You complete me.

Two Major Types of Bonding Ionic Bonding forms ionic compounds transfer of e- Covalent Bonding forms molecules sharing e-

One minor type of bonding Metallic bonding Occurs between like atoms of a metal in the free state Valence e- are mobile (move freely among all metal atoms) Positive ions in a sea of electrons Metallic characteristics High mp temps, ductile, malleable, shiny Hard substances Good conductors of heat and electricity as (s) and (l)

It’s the mobile electrons that enable me-tals to conduct electricity!!!!!!

IONic Bonding electrons are transferred between valence shells of atoms ionic compounds are made of ions NOT MOLECULES ionic compounds are called Salts or Crystals

[METALS ]+ [NON-METALS ]- IONic bonding Always formed between metals and non-metals [METALS ]+ [NON-METALS ]- Lost e- Gained e-

IONic Bonding Electronegativity difference > 2.0 Look up e-neg of the atoms in the bond and subtract NaCl CaCl2 Compounds with polyatomic ions NaNO3

Properties of Ionic Compounds SALTS Crystals hard solid @ 22oC high mp temperatures nonconductors of electricity in solid phase good conductors in liquid phase or dissolved in water (aq)

Covalent Bonding Pairs of e- are shared between non-metal atoms molecules Pairs of e- are shared between non-metal atoms electronegativity difference < 2.0 forms polyatomic ions

Always remember atoms are trying to complete their outer shell! The number of electrons the atoms needs is the total number of bonds they can make. Ex. … H? O? F? N? Cl? C? one two one three one four

Methane CH4 This is the finished Lewis dot structure How did we get here?

Types of Covalent Bonds NON-Polar bonds Electrons shared evenly in the bond E-neg difference is zero Between identical atoms Diatomic molecules

Types of Covalent Bonds Polar bond Electrons unevenly shared E-neg difference greater than zero but less than 2.0 closer to 2.0 more polar more “ionic character”

non-polar MOLECULES Sometimes the bonds within a molecule are polar and yet the molecule is non-polar because its shape is symmetrical. H C Draw Lewis dot first and see if equal on all sides

Polar molecules (a.k.a. Dipoles) Not equal on all sides Polar bond between 2 atoms makes a polar molecule asymmetrical shape of molecule

H Cl + -

Water is asymmetrical + + H O -

Water is a bent molecule H H

Making sense of the polar non-polar thing BONDS Non-polar Polar Identical Different MOLECULES Non-polar Polar Symmetrical Asymmetrical

IONIC bonds …. Ionic bonds are so polar that the electrons are not shared but transferred between atoms forming ions!!!!!!

The End