SBI4U: MOLECULAR POLARITY

·  Molecular polarity is dependent on the difference in______between atoms in a compound and the asymmetry of the compound's structure.

·  For example, a molecule of water is ______because of the ______sharing of its electrons in a "bent" structure,

·  methane (_____) is considered ______because the ______the electrons with the hydrogen atoms almost ______

·  ______aren't always shared equally between two bonding atoms: one atom might exert more of a force on the electron cloud than the other.

·  This "pull" is termed ______and measures the attraction for electrons a particular atom has.

·  The unequal sharing of electrons within a bond leads to the formation of an electric dipole: a separation of ______and negative electric charge.

·  Fractional charges are denoted as δ+ (______plus) and δ− (______minus)

A: Polar molecules

Examples of common household polar molecules include ______(household table sugar). Sugars have many polar oxygen–hydrogen (______) groups and are overall highly ______. Circle the hydroxyl groups in the pictures below

Due to the polar nature of the water molecule (H2O) itself, polar molecules are generally able to dissolve in water.

B. Non-polar molecules

A molecule may be ______either because there is (almost) no polarity in the bonds (when there is an ______sharing of electrons between two different atoms) or because of the symmetrical arrangement of polar bonds.

Examples of household non-polar compounds include fats and oils. Therefore, most non-polar molecules are not water soluble at room temperature.

In methane, the four C–H bonds are arranged tetrahedrally around the ______atom. Each bond has polarity (though not very strong). However, the bonds are arranged symmetrically so there is no overall dipole in the molecule.

This classification table gives a good general understanding of predicting polarity

Formula / Description / Example
Polar / AB / Linear Molecules / CO
HAx / Molecules with a single H / HF
AxOH / Molecules with an OH at one end / C2H5OH
OxAy / Molecules with an O at one end / H2O
NxAy / Molecules with an N at one end / NH3
Non-polar / A2 / Diatomic molecules of the same element / O2
CxAy / Most carbon compounds ______