Presentation on theme: "Polar Covalent Bonds Trends in the Periodic Table and Bonding."— Presentation transcript:
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. The atoms achieve a stable outer electron arrangement (a noble gas arrangement) by sharing electrons Both nuclei try to pull the electrons towards themselves 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.
Covalent Bonding Picture a tug-of-war: If both teams pull with the same force the mid-point of the rope will not move.
Pure 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. HH e e
Covalent Bonding 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.
Polar Covalent Bond 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.
Polar Covalent Bond e.g. Hydrogen Iodide If hydrogen iodide contained a pure covalent bond, the electrons would be shared equally as shown above. However, iodine has a higher electronegativity and pulls the bonding electrons towards itself (winning the tug-of-war) This makes iodine slightly negative and hydrogen slightly positive. This is known as a dipole. H I e e δ-δ- δ+δ+
Polar Covalent Bond In general, the electrons in a covalent bond are not equally shared. e.g. δ- indicates where the bonding electrons are most likely to be found C Cl Electronegativities δ-δ- δ+δ+
Polar Covalent Bond Consider the polarities of the following bonds: Bond Increasing Polarity Electronegativities Difference O H C Cl P H P H C Cl δ-δ- δ+δ+ O H δ-δ- δ+δ+ Complete a similar table for C-N, C-O and P-F bonds. 2.2