Polar Covalent Bonds. Trends in the Periodic Table and Bonding. -. -. -. -. +. +. +. +. Covalent Bonding. A covalent bond is a shared pair of electrons electrostatically attracted to the positive nuclei of two atoms. Both nuclei try to pull the electrons towards themselves .
Trends in the Periodic Table and Bonding
A covalent bond is a shared pair of electrons electrostatically attracted to the positive nuclei of two atoms.
Both nuclei try to pull the electrons towards themselves
The atoms achieve a stable outer electron arrangement (a noble gas arrangement) by sharing electrons.
This is like a tug-of-war where both sides are pulling on the same object.
It creates a strong bond between the two atoms.
Picture a tug-of-war:
If both teams pull with the same force the mid-point of the rope will not move.
ePure Covalent Bond
This even sharing of the rope can be compared to a pure covalent bond, where the bonding pair of electrons are held at the mid-point between the nuclei of the bonding atoms.
What if it was an uneven tug-of-war?
The team on the right are far stronger, so will pull the rope harder and the mid-point of the rope will move to the right.
A polar covalent bond is a bond formed when the shared pair of electrons in a covalent bond are not shared equally.
This is due to different elements having different electronegativities.
IPolar Covalent Bond
e.g. Hydrogen Iodide
If hydrogen iodide contained a pure covalent bond, the electrons would be shared equally as shown above.
This makes iodine slightly negative and hydrogen slightly positive. This is known as a dipole.
However, iodine has a higher electronegativity and pulls the bonding electrons towards itself
(winning the tug-of-war)
ElectronegativitiesPolar Covalent Bond
In general, the electrons in a covalent bond are not equally shared.
δ- indicates where the bonding electrons are most likely to be found.
δ+Polar Covalent Bond
Consider the polarities of the following bonds:
Complete a similar table for C-N, C-O and P-F bonds.