Ch10-COVALENT BONDING

Covalent bonds

valence electrons are shared to form molecules

resonance

Molecule or ion with multiple possible lewis structures that differ only in placement of multiple bonds or lone pairs

delocalized bond

double bond shared among all possible locations

resonance hybrid

shows delocalized bond as dashed line

electronegativity

• ability of an atom to attract shared electrons

• The greater electronegativity, the more strongly the atom attracts bonding electrons to itself

• Increase left to right, decrease down, noble gasses have no value

• Elements with higher electronegativity are less likely to share electrons and will be the outer atoms

formal charge

• Compares an atoms electron status in the molecule to the number of valence electrons of the atom

• FC= #Ve^- - lone pairs-bonds

• The most likely structure is the one with lowest formal charge

Exceptions to octet rule

• Hydrogen has less than an octet

• Elements past period 3 can form more than 4 bonds

polar covalent bonds

• unequal sharing of electrons, characterized by a separation of partial charges

• Uneven distribution causes the more electronegative atom to have a partial negative charge and the less electronegative atom to have a partial positive charge

why are polar covalent bonds dipoles

they have equal and opposite charges separated by distance

dipole moment

measures the separation of positive and negative charges, indicating its overall polarity