Chemical Bonding: Ionic Bonds & Lewis Diagrams

Study Notes

Ionic bonding involves the transfer of electrons between atoms, forming ions.
Atoms gain or lose electrons to achieve a stable electron configuration (usually a full outer shell).
Metals tend to lose electrons, forming positive ions (cations).
Nonmetals tend to gain electrons, forming negative ions (anions).
The electrostatic attraction between oppositely charged ions forms the ionic bond.
Ionic compounds are typically solid at room temperature.
Ionic compounds generally have high melting points.
Ionic compounds are often soluble in water.
Ionic compounds conduct electricity when melted or dissolved in water (because ions are free to move).

Lewis diagrams depict only the valence electrons of an atom.
Valence electrons are the outermost electrons involved in chemical bonding.
Dots are placed around the element symbol, one per valence electron.
Dots are spread evenly over the four sides of the symbol, and pairing begins only after each side has at least one dot.
The arrangement of valence electrons helps predict how atoms will bond.

Electronegativity measures an atom's ability to attract electrons in a chemical bond.
Electronegativity follows a periodic trend, with electronegativity increasing across a period and decreasing down a group.
Fluorine is the most electronegative element.
Differences in electronegativity determine the type of chemical bond formed.
A large difference in electronegativity between two bonded atoms favors ionic bonding.
A smaller difference favors covalent bonding.

Property	Ionic Compound	Covalent Compound
State at room temperature	Typically solid	Can be solid, liquid, or gas
Melting point	High	Low
Electrical conductivity as a liquid	Conducts electricity	Does not conduct electricity
Solubility in water	Often soluble	Can be soluble or insoluble
Electrical conductivity when dissolved in water	Conducts electricity	Can conduct or not conduct electricity

Atoms combine to form molecules to gain stability.
When two atoms combine, the valence electrons interact.
A chemical bond forms if the new arrangement of valence electrons has lower energy than the original arrangement.
Ionic bonding is influenced by the difference in electronegativity values (a measure of an atom's ability to attract electrons).