Which element is known as the hardest in terms of electronegativity?

Fluorine is widely recognized as the element with the highest electronegativity on the Pauling scale, with a value of 4.0. Electronegativity is a measure of the tendency of an atom to attract electrons in a chemical bond. In the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group.

Fluorine, being positioned at the top right of the periodic table among the nonmetals, exemplifies this trend perfectly. It has a very small atomic radius, which leads to a strong effective nuclear charge that attracts the bonding electrons more strongly than any other element. This property makes fluorine not just highly electronegative but also makes it highly reactive, particularly with alkali and earth alkaline metals.

Oxygen, chlorine, and nitrogen have electronegativities lower than that of fluorine; for instance, oxygen is 3.5, chlorine is 3.0, and nitrogen is 3.0 as well. Thus, fluorine stands out as the hardest element in terms of electronegativity due to its extreme ability to attract electrons compared to these other elements.