The layout of this table is based on mathematical intuition as well as predictions for how atoms in 2d would behave.
INTERESTING ELEMENTS:
Hydrogen, Helium - The first two elements, with very similar behavior to in 3d. In all dimensions, there are two elements in period 1.
Carbon - Makes 5 bonds in a pyrochoric arrangement, similar to how 3d carbon makes 4 bonds in a tetrahedral arrangement.
Nitrogen, Ridogen - Two nitrogen-type elements. One can make 4 bonds, the other, like 3d nitrogen, can make 3. Both, as nonmetals, would appear in organic molecules.
Azimovium - Basically the stereotypical fantasy metal. It's in with the strong metals like iron, titanium, and the rare earths, so it only makes sense. It's named after a friend of mine who made a sci-fi setting.
Iron - Still the highest element formed by stars, because I said so.
Majestazium - A strongly magnetic metal similar to iron or nickel.
Aphirum - Takes lead's spot as heaviest stable element.
Bismuth and onwards - The half-lives of all these elements are probably very different due to nucleus structures. In particular I imagine bismuth being somewhat more radioactive than in our world (but still largely stable on geologic timescales). The half-lives of elements are basically random without getting into anything too crazy, so I feel like it's fine to arbitrarily assign them.
The "water, ammonia, methane" group gains another member: TH3 (ridane), with properties somewhat between 3d-ammonia and water (while 4d-ammonia has properties between 3d-ammonia and methane).