update grace period

Author: DanielYang59

docs/compatibility.md

@@ -697,12 +697,19 @@ def is_post_transition_metal(self) -> bool:
 
     @property
     def is_rare_earth_metal(self) -> bool:
-        """True if element is a rare earth metal, including Scandium (Sc),
-        Yttrium (Y), Lanthanides (La) series and Actinides (Ac) series.
+        """True if element is a rare earth metal, Lanthanides (La) series and Actinides (Ac) series.
+
+        WARNING: This property would be updated to include Scandium (Sc) and
+        Yttrium (Y) after 2025-05-15.
 
         Reference: https://en.wikipedia.org/wiki/Rare-earth_element.
         """
-        return self.is_lanthanoid or self.is_actinoid or self.symbol in {"Sc", "Y"}
+        warnings.warn(
+            "Y and Sc would be considered rare earth metal after 2025-05-15.",
+            stacklevel=2,
+        )
+
+        return self.is_lanthanoid or self.is_actinoid  # or self.symbol in {"Sc", "Y"}
 
     @property
     def is_metal(self) -> bool: