diff --git a/src/nomad_simulations/atoms_state.py b/src/nomad_simulations/atoms_state.py
index 5584f913..0ed6f53b 100644
--- a/src/nomad_simulations/atoms_state.py
+++ b/src/nomad_simulations/atoms_state.py
@@ -627,31 +627,49 @@ class AtomsState(ArchiveSection):
         sub_section=HubbardInteractions.m_def, repeats=False
     )
 
-    def resolve_chemical_symbol_and_number(self, logger: BoundLogger) -> None:
+    def resolve_chemical_symbol(self, logger: BoundLogger) -> Optional[str]:
         """
-        Resolves the chemical symbol from the atomic number and viceversa.
+        Resolves the `chemical_symbol` from the `atomic_number`.
 
         Args:
             logger (BoundLogger): The logger to log messages.
+
+        Returns:
+            (Optional[str]): The resolved `chemical_symbol`.
         """
-        f = lambda x: tuple(map(bool, x))
-        if f((self.chemical_symbol, self.atomic_number)) == f((None, not None)):
+        if self.atomic_number is not None:
             try:
-                self.chemical_symbol = ase.data.chemical_symbols[self.atomic_number]
+                return ase.data.chemical_symbols[self.atomic_number]
             except IndexError:
                 logger.error(
                     'The `AtomsState.atomic_number` is out of range of the periodic table.'
                 )
-        elif f((self.chemical_symbol, self.atomic_number)) == f((not None, None)):
+        return None
+
+    def resolve_atomic_number(self, logger: BoundLogger) -> Optional[int]:
+        """
+        Resolves the `atomic_number` from the `chemical_symbol`.
+
+        Args:
+            logger (BoundLogger): The logger to log messages.
+
+        Returns:
+            (Optional[int]): The resolved `atomic_number`.
+        """
+        if self.chemical_symbol is not None:
             try:
-                self.atomic_number = ase.data.atomic_numbers[self.chemical_symbol]
+                return ase.data.atomic_numbers[self.chemical_symbol]
             except IndexError:
                 logger.error(
                     'The `AtomsState.chemical_symbol` is not recognized in the periodic table.'
                 )
+        return None
 
     def normalize(self, archive, logger) -> None:
         super().normalize(archive, logger)
 
         # Get chemical_symbol from atomic_number and viceversa
-        self.resolve_chemical_symbol_and_number(logger)
+        if self.chemical_symbol is None:
+            self.chemical_symbol = self.resolve_chemical_symbol(logger)
+        if self.atomic_number is None:
+            self.atomic_number = self.resolve_atomic_number(logger)
diff --git a/tests/test_atoms_state.py b/tests/test_atoms_state.py
index f037e3e7..9f30e2bb 100644
--- a/tests/test_atoms_state.py
+++ b/tests/test_atoms_state.py
@@ -344,3 +344,43 @@ def test_normalize(self, hubbard_interactions):
         assert np.isclose(hubbard_interactions.u_effective.to('eV').magnitude, 1.0)
         assert np.isclose(hubbard_interactions.u_interaction.to('eV').magnitude, 3.0)
         assert hubbard_interactions.slater_integrals is None
+
+
+class TestAtomsState:
+    """
+    Tests the `AtomsState` class defined in atoms_state.py.
+    """
+
+    logger = logging.getLogger(__name__)
+
+    @staticmethod
+    def add_element_information(atom_state, quantity_name, value) -> None:
+        setattr(atom_state, quantity_name, value)
+
+    @pytest.fixture(autouse=True)
+    def atom_state(self) -> AtomsState:
+        return AtomsState()
+
+    @pytest.mark.parametrize(
+        'chemical_symbol, atomic_number',
+        [
+            ('Fe', 26),
+            ('H', 1),
+            ('Cu', 29),
+            ('O', 8),
+        ],
+    )
+    def test_chemical_symbol_and_atomic_number(
+        self, atom_state, chemical_symbol, atomic_number
+    ):
+        """
+        Test the `chemical_symbol` and `atomic_number` resolution for the `AtomsState` section.
+        """
+        # Testing `chemical_symbol`
+        self.add_element_information(atom_state, 'chemical_symbol', chemical_symbol)
+        resolved_atomic_number = atom_state.resolve_atomic_number(self.logger)
+        assert resolved_atomic_number == atomic_number
+        # Testing `atomic_number`
+        self.add_element_information(atom_state, 'atomic_number', atomic_number)
+        resolved_chemical_symbol = atom_state.resolve_chemical_symbol(self.logger)
+        assert resolved_chemical_symbol == chemical_symbol