The Alchemical Symbols block spans U+1F700–U+1F77F, 128 codepoints in Plane 1 (Supplementary Multilingual Plane). 124 are assigned in Unicode 16.0; the other 4 are reserved for future characters.
All of its characters have the script value Common: they are shared across writing systems rather than tied to one.
By general category: 124 other symbols (So).
The first 116 arrived in Unicode 6.0 (2010); later additions came in 15.0 (8).
Because it lies outside the BMP, every character here takes four bytes in UTF-8 and a surrogate pair in UTF-16.