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:
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
- S must gain
- 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
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
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
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
Convenient way of showing ionic or covalent bonds Convenient way of showing ionic or covalent bonds
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
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-
Polyatomic ion: Polyatomic ion: Sodium carbonate (Na2CO3)
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