Electronegativity

Electronegativity

The ability of an atom to attract the bonding electrons in a covalent bond.

What scale is used to measure electronegativity

Pauling scale

Which element is the most electronegative and what is its electronegativity

Fluorine, 4.0

Periodic trend of electronegativity

Increases across period and decreases down groups (excluding the noble gases).

Non-polar bonds

When 2 atoms that are covalently bonded have the same or similar electronegativities, they attract the bonding electrons equally and so share the electrons equally.

Polar bonds

When 2 atoms that are covalently bonded have different electronegativities, the more electronegative atom attracts the bonding electrons more, so the bonding electrons are unevenly shared between the atoms.

In a polar bond, which atom has which partial charge

More electronegative atom has partial negative charge. Less electronegative atom has partial positive charge.

Dipole

A difference in charge between the 2 atoms caused by a shift in electron density.

How is a polar bond denoted

Using an arrow pointing towards the more electronegative atom.

What must the difference in electronegativity be greater than for a bond to be polar

0.4

Polar molecules

Molecules with an overall dipole

How can a molecule contain polar bonds but not be polar itself

If the dipoles point in opposite directions, they will cancel out