How is electronegativity defined?

Electronegativity is best defined as the relative attraction of an atom for shared pairs of electrons. This concept is fundamental in understanding how atoms bond with one another and interact in chemical reactions. Atoms with high electronegativity have a strong tendency to attract electrons toward themselves when they are part of a compound. This property significantly influences the polarity of bonds formed between atoms; for example, in a polar covalent bond, the more electronegative atom will attract the shared electrons more closely, creating a partial negative charge, while the less electronegative atom will have a partial positive charge.

In contrast to other definitions listed, the ability of an atom to lose electrons relates more closely to ionization energy rather than electronegativity. The total number of protons in an atom is related to its atomic number and defines the element itself, rather than the property of electronegativity. Lastly, measuring an element's mass in a compound pertains to molar mass or molecular weight, which is unrelated to the attraction of electrons. Thus, the correct choice effectively encapsulates the essence of what electronegativity signifies in chemistry.