Final answer:
The trend for decreasing electronegativity on the periodic table is down a group, where it decreases from top to bottom.
Step-by-step explanation:
The directional trend for decreasing electronegativity on the periodic chart is that electronegativity decreases from top to bottom within a group. This tendency can be explained by an increase in atomic size as one moves down a group, which makes the pull of the nucleus on the bonding electrons less effective. Conversely, electronegativities generally increase from left to right across a period, which is due to an increase in nuclear charge and a decrease in atomic size.
Therefore, the correct answer to the question 'What is the directional trend for decreasing electronegativity on the periodic chart?' is (d) Decreases from top to bottom.