Answer: The most electronegative element is fluorine.

This is because the atomic electron density of fluorine atoms are high, making it difficult to pull electrons off them. Fluorine bonds very easily with other elements due to its electronegativity, which is why it’s often used for chemical compounds in glasses, plastics, etcetera. Extremely reactive with water and oxygen. And while many solid materials are classified as “non-metals” or “metalloids“, there are special exceptions made for fluorine which belong to neither class – Fluorides have properties of both non-metals and metals – a curious exception!