3.1 electronegativity and bonding

Define electronegativity

The ability of an atom to attract a pair of electrons towards itself in a covalent bond

State the factors affecting electronegativity

1. Nuclear charge

2. Atomic radius

3. Shielding

How does nuclear charge affect electronegativity?

• An increase in the number of protons leads to an increase in nuclear attraction for the electrons in the outer shells

• Therefore, an increased nuclear charge results in an increased electronegativity

How does shielding affect electronegativity

the addition of extra shells and subshells in an atom will cause the outer electrons to experience less of the attractive force of the nucleus

• Thus, an increased number of inner shells and subshells will result in a decreased electronegativity

How does atomic radius affect electronegativity?

Electrons closer to the nucleus are more strongly attracted towards the nucleus.

Therefore, an increases atomic radius leads to decreased electronegativity.

Explain the trend in electronegativity down the group

• There is a decrease in electronegativity down the group

• Number of shells increases

• More shielding

• Atomic radius increases

• Increase in nuclear charge is negligible

• Less attraction between nucleus and bonding electrons

Explain the trend of electronegativity across a period

• electronegativity increases across a period

• Nuclear charge increases

• Atomic radius decreases

• Greater attraction between nucleus and bonding electrons

How are single covalent bonds formed?

Sharing pair of electrons between 2 atoms

If electronegativities are the same..

Pure non-polar covalent bond

If electronegativities are slightly different

Polar covalent bond

If electronegativities are very different

Ionic bond

If electronegativity difference is large but only non-metals are involved…

Polar covalent