Final answer:
As the electronegativity of a negatively charged atom decreases from right to left across a period on the periodic table, its nucleophilicity generally increases since it becomes less intent on attracting electron pairs and more willing to donate them.
Step-by-step explanation:
The question relates to how the nucleophilicity of a negatively charged atom changes as its electronegativity decreases across a period of the periodic table from right to left. As electronegativity decreases, an atom becomes less capable of attracting bonding electron pairs towards itself. Nucleophilicity refers to the tendency of an atom or molecule to donate an electron pair during a chemical reaction to form a covalent bond. This means that as electronegativity decreases, an atom generally becomes more nucleophilic because it is less interested in attracting electron pairs and more willing to donate them to form bonds.
Considering the periodic trends, electronegativity increases from left to right across a period. Therefore, if an atom moves from right to left, it becomes less electronegative and, in turn, its nucleophilicity increases. So, the nucleophilicity of a negatively charged atom would generally increase as its electronegativity decreases from right to left across a period.