Types of Bonds and Molecular Polarity

A set of vocabulary flashcards covering chemical bond classifications (nonpolar covalent, polar covalent, and ionic), electronegativity differences, dipole moments, and factors determining molecular polarity.

Electronegativity

The ability of an atom to attract the shared electrons in a chemical bond. Fluorine has the highest value, while non-metals generally have higher values and metals generally have lower values.

Difference in Electronegativity ($\Delta\text{EN}$)

The absolute value calculated as $|\text{EN}_1 - \text{EN}_2|$ using values from the periodic table, used to predict the type of bond present between two atoms.

Nonpolar Covalent Bond

A bond that occurs when two atoms have similar electronegativities (a difference of $0 - 0.5$) and therefore share electrons approximately equally.

Polar Covalent Bond

A bond that occurs when two atoms have different electronegativities (a difference of $0.5 - 1.7$), causing the atom with greater electronegativity to attract the shared electrons more strongly so electrons are shared unequally.

Ionic Bond

A chemical bond formed when there is a large electronegativity difference ($> 1.7$) typically between a metal and a nonmetal, resulting in the transfer of electrons rather than sharing.

Partial Charge

A small, uneven charge that develops on an atom when electrons are shared unequally in a covalent bond, resulting in a partial negative charge ($\delta-$) on the more electronegative atom and a partial positive charge ($\delta+$) on the less electronegative atom.

Dipole Moment

A separation of charge occurring when there is an uneven distribution of charge in a bond or molecule, creating a slightly positive end and a slightly negative end. It is represented by an arrow pointing from the partial positive end ($\delta+$) toward the partial negative end ($\delta-$).

Nonpolar Molecule

A molecule that has no overall dipole moment, which occurs either when its bonds are nonpolar or when it has a symmetrical shape where equal bond dipoles cancel each other out (such as linear $CO_2$).

Polar Molecule

An asymmetrical molecule containing polar bonds whose individual bond dipoles do not cancel each other out, resulting in a combined net dipole moment across the molecule (such as bent $H_2O$).

Linear Molecular Shape (Carbon Dioxide, $CO_2$)

A symmetrical molecular geometry where two polar $C=O$ bonds are oriented $180^\circ$ apart, causing the two equal bond dipoles to point in opposite directions and cancel each other out, making the overall molecule nonpolar.

Bent Molecular Shape (Water, $H_2O$)

An asymmetrical molecular geometry where the two polar $O-H$ bond dipoles do not point in opposite directions and cannot cancel out, creating a net dipole toward the oxygen atom and making the molecule polar.