What is periodic-table intended for? The tag wiki excerpt is not very helpful as it just describes what the periodic table is.
The periodic table is a systematic arrangement of the known chemical elements in order of atomic number. The elements are arranged in groups on the basis of similarity in chemical and physical properties.
I consistently find myself retagging periodic-table questions (about 90) with periodic-trends (about 80) which is usually a more appropriate tag (example here) although a sizeable number of questions have both tags (about 30).
Can we agree on a scope for this tag and write a better tag wiki (and maybe then gradually remove it from inappropriate questions).