Electronegativity and polarity

What is electronegativity

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

What are the three factors that affect electronegativity

• Nuclear charge

• Distance from nucleus (Atomic radius)

• Electron shielding

How does nuclear charge affect electronegativity

Nuclear charge is the number of protons in the nucleus so if that increases nuclear charge increases therefore, causing an increase attraction between positive nucleus and bonding pair of electrons. So, electronegativity increases.

How does distance from nucleus affect electronegativity

As distance increases between nucleus and bonding pairs of electrons increases, attraction between them decreases, so electronegativity decreases

How does electron shielding affect electronegativity

Number of electron shells increases, so more electron shielding reducing attraction between nucleus and bonding pair of electrons, so electronegativity decreases.

Why does electronegativity decrease as you go down a group

Atoms have more electron shells, so distance between nucleus and bonding pair of electrons increases. There is also electron shielding from inner shells, reducing attraction between nucleus and bonding pair of electrons. Although, nuclear charge increases, the increased shielding and distance has a greater affect, so electronegativity decreases.

Why does electronegativity increase as you go across a group

Nuclear charge increases as number of protons increases. Distance between the nucleus and bonding pair of electrons stays roughly the same as electrons are added to the same shells, and electron shielding remains similar. As nuclear charge increases and distance and electron shielding stay relatively similar attraction between the nucleus and bonding pair of electrons increases, so electronegativity increases.

Using electronegativity to estimate type of bonding

An electronegativity difference of 0 results in a covalent bond. An electronegativity difference of 0-1.8 it is polar covalent, and any higher than 1.8 it is ionic.

What is a dipole

A dipole is a separation of charge caused by an uneven distribution of electron density in a bond or molecule.

What is a non-polar bond

Bonded electron pair is shared equally as bonded atoms are the same, so there is a pure covalent bond, and the bonded atoms have the same or similar electronegativity

What is a polar bond

Bonded electron pair is shared unequally between bonded atoms as they are the different and have different electronegativity

What is bond dipole

A bond dipole is a partial separation of charge across a single covalent bond caused by an electronegativity difference

What is a molecular dipole

This is the overall separation of charge across a molecule caused by polar bonds arrange asymmetrically, so bond dipoles do not cancel

Why is H₂O polar

• Unsymmetrical shape

• Dipoles do not cancel out so has an overall dipole