diff --git a/pyproject.toml b/pyproject.toml
index f498789..860ac46 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,7 +31,10 @@ classifiers = [
 ]
 
 dependencies = [
-    "steer-core==0.2.19",
+    # Compatible-release range, not an exact pin: an exact pin means a steer-core
+    # security patch cannot be installed without rebuilding this package too.
+    # A deploy's reproducibility comes from its vendored wheel set, not from here.
+    "steer-core>=0.2.22,<0.3",
 ]
 
 [project.optional-dependencies]
diff --git a/steer_materials/Atoms.py b/steer_materials/Atoms.py
new file mode 100644
index 0000000..9806d7e
--- /dev/null
+++ b/steer_materials/Atoms.py
@@ -0,0 +1,178 @@
+# SPDX-FileCopyrightText: 2024-2026 Stanford University
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+from steer_core.Constants.Units import *
+from steer_core.Mixins.TypeChecker import ValidationMixin
+from steer_core.Mixins.Serializer import SerializerMixin
+from steer_core.Mixins.Dunder import DunderMixin
+from steer_core.Mixins.Propagation import PropagationMixin
+
+from steer_core.Decorators.General import recalculate
+
+from steer_core.Constants.Periodic_table import (
+    atomic_numbers_to_symbols,
+    atomic_numbers_to_names,
+    atomic_numbers_to_masses
+)
+
+from steer_core.Constants.Units import AU_TO_KG, KG_TO_AU
+
+class Atom(
+    ValidationMixin, 
+    SerializerMixin, 
+    DunderMixin, 
+    PropagationMixin
+):
+    
+    def __init__(
+            self, 
+            symbol: str, 
+            atomic_mass: float = None,
+            charge: float = 0.0
+        ):
+
+        self._update_properties = False
+
+        self.symbol = symbol
+        self.atomic_mass = atomic_mass
+        self.charge = charge
+
+        self._calculate_all_properties()
+        self._update_properties = True
+
+    def _calculate_all_properties(self):
+        """
+        Calculate all properties of the atom based on the provided information.
+        """
+        self._calculate_mass_from_symbol()
+        self._calculate_name_from_symbol()
+        self._calculate_atomic_number_from_symbol()
+
+    def _calculate_mass_from_name(self):
+        """
+        Calculate the atomic mass based on the atom's name.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_names.items()}[self._name]
+        self._atomic_mass = atomic_numbers_to_masses[atomic_number] * AU_TO_KG
+
+    def _calculate_symbol_from_name(self):
+        """
+        Calculate the atomic symbol based on the atom's name.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_names.items()}[self._name]
+        self._symbol = atomic_numbers_to_symbols[atomic_number]
+
+    def _calculate_atomic_number_from_name(self):
+        """
+        Calculate the atomic number based on the atom's name.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_names.items()}[self._name]
+        self._atomic_number = atomic_number
+
+    def _calculate_mass_from_symbol(self):
+        """
+        Calculate the atomic mass based on the atom's symbol.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_symbols.items()}[self._symbol]
+        self._atomic_mass = atomic_numbers_to_masses[atomic_number] * AU_TO_KG
+
+    def _calculate_name_from_symbol(self):
+        """
+        Calculate the atomic name based on the atom's symbol.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_symbols.items()}[self._symbol]
+        self._name = atomic_numbers_to_names[atomic_number]
+
+    def _calculate_atomic_number_from_symbol(self):
+        """
+        Calculate the atomic number based on the atom's symbol.
+        """
+        self._atomic_number = {v: k for k, v in atomic_numbers_to_symbols.items()}[self._symbol]
+
+    def _calculate_mass_from_atomic_number(self):
+        """
+        Calculate the atomic mass based on the atom's atomic number.
+        """
+        self._atomic_mass = atomic_numbers_to_masses[self._atomic_number] * AU_TO_KG
+
+    def _calculate_name_from_atomic_number(self):
+        """
+        Calculate the atomic name based on the atom's atomic number.
+        """
+        self._name = atomic_numbers_to_names[self._atomic_number]
+
+    def _calculate_symbol_from_atomic_number(self):
+        """
+        Calculate the atomic symbol based on the atom's atomic number.
+        """
+        self._symbol = atomic_numbers_to_symbols[self._atomic_number]
+
+    def _calculate_name_from_mass(self):
+        """
+        Calculate the atomic name based on the atom's atomic mass.
+        """
+        self._name = {v: k for k, v in atomic_numbers_to_masses.items()}[self.atomic_mass]
+
+    def _calculate_symbol_from_mass(self):
+        """
+        Calculate the atomic symbol based on the atom's atomic mass.
+        """
+        atomic_number = {v: k for k, v in atomic_numbers_to_masses.items()}[self.atomic_mass]
+        self._symbol = atomic_numbers_to_symbols[atomic_number]
+
+    def _calculate_atomic_number_from_mass(self):
+        """
+        Calculate the atomic number based on the atom's atomic mass.
+        """
+        self._atomic_number = {v: k for k, v in atomic_numbers_to_masses.items()}[self.atomic_mass]
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    @property
+    def symbol(self) -> str:
+        return self._symbol
+
+    @property
+    def atomic_number(self) -> int:
+        return self._atomic_number
+
+    @property
+    def atomic_mass(self) -> float:
+        return round(self._atomic_mass * KG_TO_AU, 3)
+
+    @name.setter
+    @recalculate("mass_from_name")
+    @recalculate("symbol_from_name")
+    @recalculate("atomic_number_from_name")
+    def name(self, value: str):
+        self.validate_string(value, "name")
+        self._name = value
+
+    @symbol.setter
+    @recalculate("atomic_number_from_symbol")
+    @recalculate("mass_from_symbol")
+    @recalculate("name_from_symbol")
+    def symbol(self, value: str):
+        self.validate_string(value, "symbol")
+        self._symbol = value
+
+    @atomic_number.setter
+    @recalculate("symbol_from_atomic_number")
+    @recalculate("mass_from_atomic_number")
+    @recalculate("name_from_atomic_number")
+    def atomic_number(self, value: int):
+        self.validate_positive_int(value, "atomic_number")
+        self._atomic_number = value
+
+    @atomic_mass.setter
+    @recalculate("name_from_mass")
+    @recalculate("symbol_from_mass")
+    @recalculate("atomic_number_from_mass")
+    def atomic_mass(self, value: float):
+        self.validate_positive_float(value, "atomic_mass")
+        self._atomic_mass = value * AU_TO_KG  
+
+
+
diff --git a/steer_materials/Crystal.py b/steer_materials/Crystal.py
new file mode 100644
index 0000000..e69de29
diff --git a/steer_materials/__init__.py b/steer_materials/__init__.py
index 2c61630..eabc785 100644
--- a/steer_materials/__init__.py
+++ b/steer_materials/__init__.py
@@ -1,5 +1,5 @@
 # SPDX-FileCopyrightText: 2024-2026 Stanford University
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-__version__ = "0.1.45"
+__version__ = "0.1.48"
 
diff --git a/test/test_atoms.py b/test/test_atoms.py
new file mode 100644
index 0000000..6b1c7c0
--- /dev/null
+++ b/test/test_atoms.py
@@ -0,0 +1,40 @@
+import unittest
+from steer_core.Constants.Units import AU_TO_KG
+
+from steer_materials.Atoms import Atom
+
+
+class TestAtom(unittest.TestCase):
+
+    def setUp(self):
+        self.atom = Atom(symbol="Pu", atomic_mass=244.0)
+
+    def test_atom_properties(self):
+        self.assertEqual(self.atom.name, "Plutonium")
+        self.assertEqual(self.atom.symbol, "Pu")
+        self.assertEqual(self.atom.atomic_number, 94)
+        self.assertAlmostEqual(self.atom._atomic_mass, 244.0 * AU_TO_KG) 
+
+    def test_atomic_mass_conversion(self):
+        # Test that the atomic mass is correctly converted to kg
+        expected_mass_kg = 244.0 * AU_TO_KG
+        self.assertAlmostEqual(self.atom._atomic_mass, expected_mass_kg)
+
+    def test_name_setter(self):
+        self.atom.name = "Uranium"
+        self.assertEqual(self.atom.symbol, "U")
+        self.assertEqual(self.atom.atomic_number, 92)
+        self.assertAlmostEqual(self.atom._atomic_mass, 238.02891 * AU_TO_KG)
+
+    def test_mass_setter(self):
+        self.atom.atomic_mass = 238.02891
+        self.assertAlmostEqual(self.atom._atomic_mass, 238.02891 * AU_TO_KG)
+        self.assertEqual(self.atom.symbol, "U")
+        self.assertEqual(self.atom.atomic_number, 92)
+
+    def test_symbol_setter(self):
+        self.atom.symbol = "U"
+        self.assertEqual(self.atom.name, "Uranium")
+        self.assertEqual(self.atom.atomic_number, 92)
+        self.assertAlmostEqual(self.atom._atomic_mass, 238.02891 * AU_TO_KG)
+