Instead of stating the trend
for [a property], walk me
through the two competing
effects that produce it, then
let me predict down a group
and across a period.

Reason Out a Periodic Trend

Two competing effects, then you make the prediction.

Prompt

Rather than telling me the trend for [electronegativity, atomic radius, ionisation energy], walk me through the two competing effects that produce it, then let me predict what happens down a group and across a period.