diff --git a/gui/tests/artifacts.js b/gui/tests/artifacts.js
index 42adc8be2020021882fd8cf267d09b70654e8e7e..e63552ff77ba632c34fce8ab2685288ec03c0a28 100644
--- a/gui/tests/artifacts.js
+++ b/gui/tests/artifacts.js
@@ -58346,7 +58346,10 @@ window.nomadArtifacts = {
                   ]
                 },
                 "name": "molecular_mass",
-                "description": "Molecular mass.",
+                "description": "The mass of the most likely isotopic composition for a single molecule,\ncorresponding to the most intense ion/molecule peak in a mass spectrum.",
+                "links": [
+                  "https://en.wikipedia.org/wiki/Molecular_mass"
+                ],
                 "type": {
                   "type_kind": "numpy",
                   "type_data": "float64"
@@ -58357,6 +58360,52 @@ window.nomadArtifacts = {
                 "m_def": "nomad.metainfo.metainfo.Quantity",
                 "m_parent_index": 4,
                 "m_parent_sub_section": "quantities",
+                "m_annotations": {
+                  "eln": [
+                    {
+                      "component": "NumberEditQuantity",
+                      "defaultDisplayUnit": "g/mol"
+                    }
+                  ]
+                },
+                "name": "molar_mass",
+                "description": "The molar mass is the sum of all atomic masses of the constituent atoms in a\ncompound, measured in g/mol. In the absence of explicit isotope labelling,\naveraged natural abundance is assumed. If an atom bears an explicit isotope label,\n100%% isotopic purity is assumed at this location.",
+                "links": [
+                  "https://en.wikipedia.org/wiki/Molar_mass"
+                ],
+                "type": {
+                  "type_kind": "numpy",
+                  "type_data": "float64"
+                },
+                "unit": "gram / mole"
+              },
+              {
+                "m_def": "nomad.metainfo.metainfo.Quantity",
+                "m_parent_index": 5,
+                "m_parent_sub_section": "quantities",
+                "m_annotations": {
+                  "eln": [
+                    {
+                      "component": "NumberEditQuantity",
+                      "defaultDisplayUnit": "Da"
+                    }
+                  ]
+                },
+                "name": "monoisotopic_mass",
+                "description": "The mass of a molecule, calculated using the mass of the most abundant isotope of\neach element.",
+                "links": [
+                  "https://en.wikipedia.org/wiki/Monoisotopic_mass"
+                ],
+                "type": {
+                  "type_kind": "numpy",
+                  "type_data": "float64"
+                },
+                "unit": "dalton"
+              },
+              {
+                "m_def": "nomad.metainfo.metainfo.Quantity",
+                "m_parent_index": 6,
+                "m_parent_sub_section": "quantities",
                 "m_annotations": {
                   "eln": [
                     {
@@ -58373,7 +58422,7 @@ window.nomadArtifacts = {
               },
               {
                 "m_def": "nomad.metainfo.metainfo.Quantity",
-                "m_parent_index": 5,
+                "m_parent_index": 7,
                 "m_parent_sub_section": "quantities",
                 "m_annotations": {
                   "eln": [
@@ -58391,7 +58440,7 @@ window.nomadArtifacts = {
               },
               {
                 "m_def": "nomad.metainfo.metainfo.Quantity",
-                "m_parent_index": 6,
+                "m_parent_index": 8,
                 "m_parent_sub_section": "quantities",
                 "m_annotations": {
                   "eln": [
@@ -58409,7 +58458,7 @@ window.nomadArtifacts = {
               },
               {
                 "m_def": "nomad.metainfo.metainfo.Quantity",
-                "m_parent_index": 7,
+                "m_parent_index": 9,
                 "m_parent_sub_section": "quantities",
                 "m_annotations": {
                   "eln": [
@@ -58427,7 +58476,7 @@ window.nomadArtifacts = {
               },
               {
                 "m_def": "nomad.metainfo.metainfo.Quantity",
-                "m_parent_index": 8,
+                "m_parent_index": 10,
                 "m_parent_sub_section": "quantities",
                 "m_annotations": {
                   "eln": [
diff --git a/nomad/datamodel/metainfo/basesections.py b/nomad/datamodel/metainfo/basesections.py
index b54936d28bcc1f411f55bcdc943d53d11f921b84..942a6aecc0559ce1e35fa8a4c2837cff0ce2f45a 100644
--- a/nomad/datamodel/metainfo/basesections.py
+++ b/nomad/datamodel/metainfo/basesections.py
@@ -860,8 +860,40 @@ class PureSubstanceSection(ArchiveSection):
     )
     molecular_mass = Quantity(
         type=np.dtype(np.float64),
+        links=['https://en.wikipedia.org/wiki/Molecular_mass'],
         unit='Da',
-        description='Molecular mass.',
+        description="""
+        The mass of the most likely isotopic composition for a single molecule,
+        corresponding to the most intense ion/molecule peak in a mass spectrum.
+        """,
+        a_eln=dict(
+            component='NumberEditQuantity',
+            defaultDisplayUnit='Da',
+        ),
+    )
+    molar_mass = Quantity(
+        type=np.dtype(np.float64),
+        links=['https://en.wikipedia.org/wiki/Molar_mass'],
+        unit='g/mol',
+        description="""
+        The molar mass is the sum of all atomic masses of the constituent atoms in a
+        compound, measured in g/mol. In the absence of explicit isotope labelling,
+        averaged natural abundance is assumed. If an atom bears an explicit isotope label,
+        100%% isotopic purity is assumed at this location.
+        """,
+        a_eln=dict(
+            component='NumberEditQuantity',
+            defaultDisplayUnit='g/mol',
+        ),
+    )
+    monoisotopic_mass = Quantity(
+        type=np.dtype(np.float64),
+        links=['https://en.wikipedia.org/wiki/Monoisotopic_mass'],
+        unit='Da',
+        description="""
+        The mass of a molecule, calculated using the mass of the most abundant isotope of
+        each element.
+        """,
         a_eln=dict(
             component='NumberEditQuantity',
             defaultDisplayUnit='Da',
@@ -1449,6 +1481,8 @@ class PubChemPureSubstanceSection(PureSubstanceSection):
             'IUPACName': 'iupac_name',
             'MolecularFormula': 'molecular_formula',
             'ExactMass': 'molecular_mass',
+            'MolecularWeight': 'molar_mass',
+            'MonoisotopicMass': 'monoisotopic_mass',
             'InChI': 'inchi',
             'InChIKey': 'inchi_key',
             'IsomericSMILES': 'smile',
@@ -1459,6 +1493,8 @@ class PubChemPureSubstanceSection(PureSubstanceSection):
             'IUPACName': str,
             'MolecularFormula': str,
             'ExactMass': float,
+            'MolecularWeight': float,
+            'MonoisotopicMass': float,
             'InChI': str,
             'InChIKey': str,
             'IsomericSMILES': str,