Across a period vs. Down a group

[YashDeshmukh1D]

If we can understand that going across a period from left to right results in an increase of nuclear attraction (since no energy levels are being added to offset the increased number of protons) and that going down a group results in a decrease of nuclear attraction (since the increased energy levels lead to more shielding between electrons and nucleus), which of these is greater in strength?

For example, would boron have a greater or smaller atomic radius than chlorine?

[StephanieDoan3B]

I don't think we have to or are able to use trends to compare atoms of elements not in the same period or group.

[Mitch Walters]

This might be something that can only be known from experimental values.

[Gobinder Pandher 3J]

Typically, if we need to know, the atomic radii will be given to us already. In my high school chemistry class, if we ever compared the different ionization energies between two elements these values were usually given to us (either on the back of our periodic table or in the problem). I'd assume the same for atomic radii.