diff --git a/propka/atom.py b/propka/atom.py
index ec16046..231abb3 100644
--- a/propka/atom.py
+++ b/propka/atom.py
@@ -58,9 +58,6 @@ class Atom:
         self.z = None
         self.group = None
         self.group_type = None
-        self.group_label = None
-        self.group_model_pka = None
-        self.group_model_pka_set = None
         self.number_of_bonded_elements = {}
         self.cysteine_bridge = False
         self.bonded_atoms = []