1: Electronegativity and bond polarity

What is electronegativity?

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

How is electronegativity measured?

Pauling scale

What are the most electronegative elements?

Fluorine, oxygen, chlorine

What are the least electronegative elements?

Group one

What factors affect electronegativity?

Nuclear charge: more protons means stronger attraction between nucleus and bonding pairs of electrons

Atomic radius: closer to nucleus means stronger attraction between nucleus and bonding pair of electrons

Shielding: less electrons between nucleus and neutrons means stronger attraction between nucleus and bonding pair of electrons

What is the trend down a group?

Electronegativity decreases. Atomic radius increases so there is more shielding which means less attraction between nucleus and bonding pair of electrons.

What is the trend across a period?

Electronegativity increases because there is a larger nuclear charge and the atomic radius decreases which means as a stronger attraction between the nucleus and bonding pair of electrons

What happens if the electronegativity difference is large?

Have a much greater attraction for the shared pair so it will gain control of the bond will become ionic

What happens to the bonded electron pair in a non-polar bond?

It’s shared equally between the bonded atoms

When will a bond be non-polar?

When the bonded atoms are the same, or the bonded atoms have a similar electronegativity

What happens to the bonded electron pair in a polar bond?

The bonded electron pairs shared unequally between the bonded atoms

When will a bond be polar? What does it result in?

Bonded atoms are different and have different electronegativity values, which results in a polar covalent bond

What is a dipole?

a separation in electrical charge, so that one atom of a polar covalent bond, or one end of a polar molecule had a small positive charge, and the other had a small negative charge

What is a permanent dipole?

a dipole in a polar covalent bonds that does not change

A polar molecule requires what?

A polar bond, dipoles that do not cancel out due to the direction, for example, H2O, and not CO2