diff --git a/src/Humanizer/Inflections/Vocabularies.cs b/src/Humanizer/Inflections/Vocabularies.cs
index 1107672ab..2aaaec8e2 100644
--- a/src/Humanizer/Inflections/Vocabularies.cs
+++ b/src/Humanizer/Inflections/Vocabularies.cs
@@ -20,6 +20,94 @@ internal static string ApplyAcronyms(string input) =>
     internal static string NormalizeAcronyms(string input) =>
         Instance.IsValueCreated ? Instance.Value.NormalizeAcronyms(input) : input;
 
+    /// <summary>
+    /// Element names ending in -ium (and aluminum) are most often uncountable
+    /// </summary>
+    internal static readonly string[] UncountableChemicalElementNames =
+    [
+        "actinium",
+        "aluminium",
+        "aluminum",
+        "americium",
+        "barium",
+        "berkelium",
+        "beryllium",
+        "bohrium",
+        "cadmium",
+        "caesium",
+        "californium",
+        "calcium",
+        "cerium",
+        "cesium",
+        "chromium",
+        "copernicium",
+        "curium",
+        "darmstadtium",
+        "dubnium",
+        "dysprosium",
+        "einsteinium",
+        "erbium",
+        "europium",
+        "fermium",
+        "flerovium",
+        "francium",
+        "gadolinium",
+        "gallium",
+        "germanium",
+        "hafnium",
+        "hassium",
+        "helium",
+        "holmium",
+        "indium",
+        "iridium",
+        "lawrencium",
+        "lithium",
+        "livermorium",
+        "lutetium",
+        "magnesium",
+        "meitnerium",
+        "mendelevium",
+        "moscovium",
+        "neodymium",
+        "neptunium",
+        "nihonium",
+        "niobium",
+        "nobelium",
+        "osmium",
+        "palladium",
+        "plutonium",
+        "polonium",
+        "potassium",
+        "praseodymium",
+        "promethium",
+        "protactinium",
+        "radium",
+        "rhenium",
+        "rhodium",
+        "roentgenium",
+        "rubidium",
+        "ruthenium",
+        "rutherfordium",
+        "samarium",
+        "scandium",
+        "seaborgium",
+        "selenium",
+        "sodium",
+        "strontium",
+        "technetium",
+        "tellurium",
+        "terbium",
+        "thallium",
+        "thorium",
+        "thulium",
+        "titanium",
+        "uranium",
+        "vanadium",
+        "ytterbium",
+        "yttrium",
+        "zirconium",
+    ];
+
     static Vocabulary BuildDefault()
     {
         var _default = new Vocabulary();
@@ -27,8 +115,8 @@ static Vocabulary BuildDefault()
         _default.AddPlural("$", "s");
         _default.AddPlural("s$", "s");
         _default.AddPlural("(ax|test)is$", "$1es");
-        _default.AddPlural("(octop|vir|alumn|fung|cact|foc|hippopotam|radi|stimul|syllab|nucle)us$", "$1i");
-        _default.AddPlural("(alias|bias|iris|status|campus|apparatus|virus|walrus|trellis)$", "$1es");
+        _default.AddPlural("(vir|alumn|fung|cact|foc|radi|stimul|syllab|nucle)us$", "$1i");
+        _default.AddPlural("(alias|bias|iris|status|campus|apparatus|virus|walrus|trellis|octopus|hippopotamus)$", "$1es");
         _default.AddPlural("(buffal|tomat|volcan|ech|embarg|her|mosquit|potat|torped|vet)o$", "$1oes");
         _default.AddPlural("([dti])um$", "$1a");
         _default.AddPlural("sis$", "ses");
@@ -50,6 +138,7 @@ static Vocabulary BuildDefault()
         _default.AddSingular("([dti])a$", "$1um");
         _default.AddSingular("(analy|ba|diagno|parenthe|progno|synop|the|ellip|empha|neuro|oa|paraly)ses$", "$1sis");
         _default.AddSingular("(.+)ves$", "$1ve");
+        _default.AddSingular("(him|her|it|my|one)selves$", "$1self");
         _default.AddSingular("(hive)s$", "$1");
         _default.AddSingular("(tive)s$", "$1");
         _default.AddSingular("(cal|dwar|el|hal|hoo|lea|loa|scar|sel|shel|thie|tur|whar|wol)ves$", "$1f");
@@ -63,9 +152,11 @@ static Vocabulary BuildDefault()
         _default.AddSingular("(shoe)s$", "$1");
         _default.AddSingular("((?<![a-z])ax|(?-i:(?<=[A-Za-z])Ax)|cris|test)es$", "$1is");
         _default.AddSingular("(octop|vir|alumn|fung|cact|foc|hippopotam|radi|stimul|syllab|nucle)i$", "$1us");
-        _default.AddSingular("(alias|bias|iris|status|campus|apparatus|virus|walrus|trellis)es$", "$1");
+        _default.AddSingular("(octop)odes$", "$1us");
+        _default.AddSingular("(alias|bias|iris|status|campus|apparatus|virus|walrus|trellis|octopus|hippopotamus)es$", "$1");
         _default.AddSingular("^(ox)en", "$1");
         _default.AddSingular("(matr|d)ices$", "$1ix");
+        _default.AddSingular("spandices$", "spandex");
         _default.AddSingular("(vert|ind)ices$", "$1ex");
         _default.AddSingular("(quiz)zes$", "$1");
         _default.AddSingular("(buz|blit|walt)zes$", "$1z");
@@ -86,6 +177,15 @@ static Vocabulary BuildDefault()
         _default.AddIrregular("foot", "feet");
         _default.AddIrregular("tooth", "teeth");
         _default.AddIrregular("curriculum", "curricula");
+        _default.AddIrregular("premium", "premiums");
+        _default.AddIrregular("stadium", "stadiums");
+        _default.AddIrregular("podium", "podiums");
+        _default.AddIrregular("ultimatum", "ultimatums");
+        _default.AddIrregular("condominium", "condominiums");
+        _default.AddIrregular("euphonium", "euphoniums");
+        _default.AddIrregular("harmonium", "harmoniums");
+        _default.AddIrregular("criterium", "criteriums"); // Note: not the same as criterion
+        _default.AddIrregular("spandex", "spandexes");
         _default.AddIrregular("database", "databases");
         _default.AddIrregular("zombie", "zombies");
         _default.AddIrregular("personnel", "personnel");
@@ -139,6 +239,11 @@ static Vocabulary BuildDefault()
         _default.AddUncountable("salmon");
         _default.AddUncountable("shrimp");
         _default.AddUncountable("someone");
+        _default.AddUncountable("himself");
+        _default.AddUncountable("herself");
+        _default.AddUncountable("itself");
+        _default.AddUncountable("myself");
+        _default.AddUncountable("oneself");
         _default.AddUncountable("swine");
         _default.AddUncountable("trout");
         _default.AddUncountable("tuna");
@@ -156,6 +261,8 @@ static Vocabulary BuildDefault()
         //Fix 1132
         _default.AddUncountable("metadata");
 
+        Array.ForEach(UncountableChemicalElementNames, _default.AddUncountable);
+
         _default.MarkRulesAsBuiltIn();
         return _default;
     }
diff --git a/tests/Humanizer.Tests/InflectorTests.cs b/tests/Humanizer.Tests/InflectorTests.cs
index 8684a8643..af5b60135 100644
--- a/tests/Humanizer.Tests/InflectorTests.cs
+++ b/tests/Humanizer.Tests/InflectorTests.cs
@@ -172,6 +172,57 @@ public void SingularizeDoesNotRewriteUnrelatedWordsEndingInMen(string word)
     public void SingularizeVesEdgeCases(string plural, string expected) =>
         Assert.Equal(expected, plural.Singularize());
 
+    [Theory]
+    [InlineData("octopuses", "octopus")]
+    [InlineData("octopi", "octopus")]
+    [InlineData("octopodes", "octopus")]
+    [InlineData("hippopotamuses", "hippopotamus")]
+    [InlineData("hippopotami", "hippopotamus")]
+    [InlineData("premiums", "premium")]
+    [InlineData("premia", "premium")]
+    [InlineData("stadiums", "stadium")]
+    [InlineData("stadia", "stadium")]
+    [InlineData("podiums", "podium")]
+    [InlineData("podia", "podium")]
+    [InlineData("ultimatums", "ultimatum")]
+    [InlineData("ultimata", "ultimatum")]
+    [InlineData("condominiums", "condominium")]
+    [InlineData("condominia", "condominium")]
+    [InlineData("euphoniums", "euphonium")]
+    [InlineData("euphonia", "euphonium")]
+    [InlineData("harmoniums", "harmonium")]
+    [InlineData("harmonia", "harmonium")]
+    [InlineData("criteriums", "criterium")]
+    [InlineData("spandexes", "spandex")]
+    [InlineData("spandices", "spandex")]
+    [InlineData("himselves", "himself")]
+    [InlineData("herselves", "herself")]
+    [InlineData("itselves", "itself")]
+    [InlineData("myselves", "myself")]
+    [InlineData("oneselves", "oneself")]
+    [InlineData("yourselves", "yourself")]
+    [InlineData("aquariums", "aquarium")]
+    [InlineData("auditoriums", "auditorium")]
+    [InlineData("consortiums", "consortium")]
+    [InlineData("symposiums", "symposium")]
+    public void SingularizeRecognizesAlternatePlurals(string plural, string singular)
+    {
+        Assert.Equal(singular, plural.Singularize());
+        Assert.Equal(singular, plural.Singularize(inputIsKnownToBePlural: false));
+    }
+
+    [Fact]
+    public void ChemicalElementNamesEndingInIumAreUncountable()
+    {
+        foreach (var element in Vocabularies.UncountableChemicalElementNames)
+        {
+            Assert.Equal(element, element.Pluralize());
+            Assert.Equal(element, element.Singularize());
+            Assert.Equal(element, element.Pluralize(inputIsKnownToBeSingular: false));
+            Assert.Equal(element, element.Singularize(inputIsKnownToBePlural: false));
+        }
+    }
+
     [Theory]
     [InlineData("a")]
     [InlineData("A")]
@@ -495,7 +546,7 @@ public IEnumerator<object[]> GetEnumerator()
 
         yield return ["louse", "lice"];
         yield return ["house", "houses"];
-        yield return ["octopus", "octopi"];
+        yield return ["octopus", "octopuses"];
         yield return ["alias", "aliases"];
         yield return ["portfolio", "portfolios"];
         yield return ["criterion", "criteria"];
@@ -567,7 +618,7 @@ public IEnumerator<object[]> GetEnumerator()
         yield return ["grass", "grass"];
         yield return ["hair", "hair"];
         yield return ["hero", "heroes"];
-        yield return ["hippopotamus", "hippopotami"];
+        yield return ["hippopotamus", "hippopotamuses"];
         yield return ["hoof", "hooves"];
         yield return ["iris", "irises"];
         yield return ["larva", "larvae"];
@@ -656,6 +707,28 @@ public IEnumerator<object[]> GetEnumerator()
 
         //Issue #1042
         yield return ["database", "databases"];
+
+        //Issue #1962
+        yield return ["premium", "premiums"];
+        yield return ["stadium", "stadiums"];
+        yield return ["podium", "podiums"];
+        yield return ["ultimatum", "ultimatums"];
+        yield return ["condominium", "condominiums"];
+        yield return ["euphonium", "euphoniums"];
+        yield return ["harmonium", "harmoniums"];
+        yield return ["criterium", "criteriums"];
+        yield return ["spandex", "spandexes"];
+        yield return ["himself", "himself"];
+        yield return ["herself", "herself"];
+        yield return ["itself", "itself"];
+        yield return ["myself", "myself"];
+        yield return ["oneself", "oneself"];
+        yield return ["yourself", "yourselves"];
+        yield return ["self", "selves"];
+        yield return ["aquarium", "aquaria"];
+        yield return ["auditorium", "auditoria"];
+        yield return ["consortium", "consortia"];
+        yield return ["symposium", "symposia"];
     }
 
     IEnumerator IEnumerable.GetEnumerator() =>