Khan academy doesn't say what the trend is going up and down groups in the periodic table.
From sources I've found online, it is debated/depends/essentially unchanged like in the image.
I think it should be left as is in the image because there are opposing effects happening: more protons added (increasing Zeff), but more electron shells being added (more shielding -> decreasing Zeff)
Also, he only says the trend that it increases from left to right.
https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:periodic-trends/v/periodic-trends-and-coulombs-law
Khan Academy may not state, though other primary sources do give a periodic trend for Zeff (UWorld, etc.).
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