Diagram that shows

Diagram that shows

• Diagram that shows

• American chemist Gilbert N. Lewis
• Dots =
• Paired dots =

• Simple way of showing electrons

• Most reactions involve only

When drawing:

• When drawing:

• Use electron configuration
• Move in clockwise direction…
• “12” = s orbital
• “3, 6, 9” = p orbitals – fill each with ONE electron before filling with pairs…
• Just like orbital filling diagram…

• Examples: draw Lewis Structures of B, N, F, Ne

Ionic bond:

• Ionic bond:

• Transfer of electrons from
• Ions form with
• Attraction between electrostatic charges is a strong force which holds atoms together

NOT A

• NOT A

• Bond not just between (for example) one sodium and one chloride

Typically

• Typically

• Metals usually

• Nonmetals usually

In almost all stable chemical compounds of representative elements, each atom attains a

• In almost all stable chemical compounds of representative elements, each atom attains a

• This concept forms the basis for our understanding of chemical bonding.

How many electrons must be gained or lost to achieve noble gas configuration?

• How many electrons must be gained or lost to achieve noble gas configuration?

• Ba must lose
• Forms the ion
• S must gain
• Forms the ion
• So…must be ratio of

Elements in a family usually form compounds with the same atomic ratios

• Elements in a family usually form compounds with the same atomic ratios

• Because they have the same number of valence electrons
• Must gain or lose the same number of electrons
• See table 11.4 pg 233

The formula for sodium oxide is Na2O. Predict the formula for

• The formula for sodium oxide is Na2O. Predict the formula for

• Sodium sulfide

Rubidium Oxide

• Rubidium Oxide

• Rubidium
• Oxygen
• So…formula must be
• This makes sense b/c rubidium is in same family as sodium

A pair of

• A pair of

• Most common type of bond

• Stronger than

• Electron orbital expands to include both nuclei

• most often found between
• Negative charges allow positive nuclei to be drawn close to each other

Atoms may share more than one pair of electrons

• Atoms may share more than one pair of electrons

• Double bond –
• Triple bond –
• Multiple bonds are

• Covalent bonding between identical atoms means electrons are shared

• Covalent bonding between different atoms leads to

The attractive force that an atom of an element has for

• The attractive force that an atom of an element has for

• Atoms have different electronegativities

• Electrons will spend more time near atom with
• So…one atom assumes a partial
• The other assumes a partial

Electronegativity trends and periodic table

• Electronegativity trends and periodic table

• See table 11.5 page 237
• Generally increases from
• Decreases
• Highest is
• Lowest is

Polarity is determined by difference in electronegativity

• Polarity is determined by difference in electronegativity

• Nonpolar covalent
• Polar covalent
• Ionic compound

If the electronegativity difference is greater than

• If the electronegativity difference is greater than

• Above

• Below

Polar bonds form between two atoms

• Polar bonds form between two atoms

• Molecules can also be polar or nonpolar

• Dipole
• Polar
• Nonpolar

Convenient way of showing ionic or covalent bonds

• Convenient way of showing ionic or covalent bonds

• Usually the single atom in a formula is the central atom

LEWIS STRUCTURES of ionic bonds

• LEWIS STRUCTURES of ionic bonds

LEWIS STRUCTURES of covalent bonds

• LEWIS STRUCTURES of covalent bonds

• Use dashes instead of dots…

Obtain the total number of valence electrons

• Obtain the total number of valence electrons

• Add the valance electrons of all atoms
• Ionic – add one electron for each negative charge and subtract one electron for each positive charge

Write the skeletal arrangement of the atoms and connect with a single covalent vond

• Write the skeletal arrangement of the atoms and connect with a single covalent vond

• Subtract two electrons for each single bond

• This gives you the net number of electrons available for completing the structure

Distribute pairs of electrons around each atom to give each atom a noble gas structure

• Distribute pairs of electrons around each atom to give each atom a noble gas structure

• If there are not enough electrons then try to form double and triple bonds

Write the Lewis Structure for methane CH4

• Write the Lewis Structure for methane CH4

Carbon Dioxide, CO2

• Carbon Dioxide, CO2

Some molecules and polyatomic ions have strange behaviors…

• Some molecules and polyatomic ions have strange behaviors…

• No single Lewis structure is consistent
• If multiple structures are possible the molecule shows

Carbonate ion, CO32-

• Carbonate ion, CO32-

Polyatomic ion:

• Polyatomic ion:

• Behaves as a single unit in many chemical reactions

• Sodium carbonate (Na2CO3)