Electronegativity across period 3
After studying this page, you should be able to:
- describe and explain the trend in electronegativity across period 3
The table shows electronegativity values for the elements Na to Ar.
Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond.
The table gives values on the Pauling scale, which have no units. Fluorine (3.98) is the most electronegative element.
Electronegativity in the periodic table
Description of trend
The graph shows how electronegativity varies across period 3:
- as the atomic number increases, the electronegativity of the elements decreases.
Explanation of this trend
Going across period 3:
- the nuclear charge increases …
- the atomic radius decreases …
- there are more electrons, but the increase in shielding is negligible because each extra electron enters the same shell …
- so electrons will be more strongly attracted to the nucleus.
In Period 3, sodium with 11 protons is the least electronegative element, and chlorine with 17 protons is the most electronegative element. You might expect argon (with 18 electrons) to be the most electronegative element in Period 3. However, it does not form covalent bonds, so it does not have an electronegativity value.