Why is fluorine more electronegative than chlorine?

Answer 1

A qualitative answer is that fluorine is more electronegative than chlorine because the outer electrons in fluorine are less "screened" from their attraction to the positive nucleus, because there are more non-valence electrons in chlorine.

Two factors affect the electronegativity of an element:

• Nuclear charge: If the element has a large nuclear charge it will attract electrons to it more readily than one with a small nuclear charge.
• The radius of the atom: If the element is small then the effect of the pull from the nucleus will be greater (due to physical distance between the nucleus and the outside of the atom and the effect of electron shielding - shells of electrons reducing the 'pulling' power of the nucleus). As we go across a period the atomic radii of the atoms decreases. As we go down a group the atomic radii of the atom increases (even though the nuclear charge also increases, the atomic radii increases to a greater extent which practically cancels out the effect of the increased nuclear charge)

Therefore the most electronegative element is Fluorine, followed by Oxygen, Nitrogen and Chlorine: F>O>N>C

Answer 2

As atoms get larger, you have two opposing effects with regard to the capacity of that atom to attract electrons. First, the electrons are going to be farther from the nucleus because there are simply more electrons surrounding the atom, and since electrons repel each other, they inevitably are going to take up more room when you have more of them. And when electrons are farther away from the nucleus which attracts them, the attraction is reduced, in proportion to the square of the distance (as described by Coulomb's Law). The other effect, as atoms grow larger, is that the nucleus has more protons in it and therefore exerts a more powerful attraction on electrons (see Coulomb's Law again). This, however, is a linear effect. It is directly proportional to the number of protons. So the decline in attraction, which is proportional to the square of the distance, is a stronger effect than the increase in attraction which is only a direct proportion to the number of protons. The net effect is that as atoms get larger, there is less attraction for electrons (in the outer shell) and consequently, less electronegativity. This is not just about the comparison of fluorine and iodine, it applies to all elements. The heavier they get, the less electronegativity they have. Another way of describing this is, every element becomes more metallic as you move toward the bottom of the Periodic Table.

Answer 3

Fluorine is more electronegative than chlorine because fluorine has a smaller atomic size and a higher effective nuclear charge. This results in a stronger attraction for electrons in the fluorine atom, making it more electronegative compared to chlorine.

Answer 4

Larger atoms gain electrons less easily. Chlorine is a larger atom than fluorine and therefore it gains the electrons needed to fill its outermost shell less easily than a fluorine atom.

Answer 5

Fluorine is more electronegative than chlorine.