Presentation on theme: "Trends in the Periodic Table and Bonding"— Presentation transcript:
1Trends in the Periodic Table and Bonding Polar Covalent Bonds
2Covalent BondingA 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-+-+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.The atoms achieve a stable outer electron arrangement (a noble gas arrangement) by sharing electrons.
3Covalent Bonding Picture a tug-of-war: If both teams pull with the same force the mid-point of the rope will not move.
4Pure Covalent BondHeHThis 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.
5Covalent 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.
6Polar Covalent BondA 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.
7Polar Covalent Bond I δ- δ+ H e.g. Hydrogen Iodide e 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)
8Polar Covalent Bond C Cl δ+ δ- In general, the electrons in a covalent bond are not equally shared.δ-δ+e.g.CCl2.53.0Electronegativitiesδ- indicates where the bonding electrons are most likely to be found.
9Polar Covalent Bond Consider the polarities of the following bonds: ElectronegativitiesDifferenceC Cl0.5P HO H1.4C Clδ-δ+O Hδ-δ+P HIncreasing PolarityComplete a similar table for C-N, C-O and P-F bonds.