CREATE TABLE table_name_6 (isotopic_mass___u__ VARCHAR, nuclide VARCHAR)

What is the isotopic mass (u) when the nuclide is 89 y?
SELECT isotopic_mass___u__ FROM table_name_6 WHERE nuclide = "89 y"
SELECT "isotopic_mass___u__" FROM "table_name_6" WHERE "89 y" = "nuclide"