10.6 Electronegativity and Bond Polarity

polar covalent bond

a covalent bond between two atoms with significantly different electronegativities, resulting in an uneven distribution of electron density

positive, negative

When representing polar covalent bonds with arrows, the positive sign on the tail shows the direction of partial _________ charge while the arrow shows the direction of partial _________ charge.

are not

Delta plus or minus signs of partially positive or negative charge ____ (are/are not) representative of an ionic bond.

electronegativity

an atom’s ability to attract electrons to itself in a covalent bond, resulting in polar and ionic bonds

bond energy

the energy required to break a bond

polar

The bond energy of a heteronuclear diatomic molecule is not necessarily the average of its homonuclear counterparts’ bond energies due to _____ (pure/polar) covalent bonding.

increases

Electronegativity generally _________ (increases/decreases) across a period in the periodic table.

decreases

Electronegativity generally _________ (increases/decreases) down a column in the periodic table.

Fluorine

________ is the most electronegative element.

Francium

_________ is the least electronegative element (electropositive).

noble gas

_______________ (alkali metal/alkaline earth metal/halogen/noble gas) atoms are not assigned electronegativity values.

inversely, less

In general, electronegativity is _________ (directly/inversely) related to atomic size; the larger the atom, the ____ (more/less) ability it has to attract electrons to itself in a chemical bond.

electronegativity difference

∆EN, value determining the degree of polarity in a chemical bond

directly

Electronegativity difference and bond polarity are _________ (directly/inversely) related.

purely, nonpolar

If two atoms with identical electronegativities form a covalent bond, they share the electrons equally, and the bond is ______ covalent or _______.

ionic

If there is a large electronegativity difference between two atoms in a bond (e.g. metal and nonmetal), the electron of the metal is almost completely transferred to the nonmetal, and the bond is _____ (ionic/covalent).

polar

If there is an intermediate electronegativity difference between the two atoms, such as between two different nonmetals, then the bond is _____ covalent.

dipole moment (μ)

measure of the separation of positive and negative charge in a molecule, quantified polarity of a bond

μ=qr

equation for magnitude of dipole moment created by separating two particles of equal but opposite charges of magnitude q by a distance r

debye (D)

unit commonly used for reporting dipole moments

1D=3.34×10^-30C*m

debye to Coulombs*meters conversion

smaller, more

The smaller the magnitude of charge separation, the _______ (larger/smaller) the dipole moment, the _____ (more/less) covalent the bond.

percent ionic character

the ratio of a bond’s actual dipole moment to the dipole moment it would have if the electron were transferred completely from one atom to the other, multiplied by 100%

• (measured dipole moment of bond)/(dipole moment if electron were completely transferred) * 100%

% ionic character = measured dipole moment of bond/dipole moment if electrons were completely transferred * 100%

percent ionic character equation

100

A bond in which an electron is completely transferred from one atom to another would have ___% ionic character, but no bond is 100% ionic.

increases

Percent ionic character generally _________ (increases/decreases) as the electronegativity difference increases.

50

In general, bonds with greater than __% ionic character are referred to as ionic bonds.