diff --git a/js/common/model/Atom.js b/js/common/model/Atom.js
index 45836c59..031f89fb 100644
--- a/js/common/model/Atom.js
+++ b/js/common/model/Atom.js
@@ -30,7 +30,7 @@ define( function( require ) {
     }, options );
 
     assert && assert( MPConstants.ELECTRONEGATIVITY_RANGE.contains( options.electronegativity ),
-      'invalid electronegativity: ' + options.electronegativity );
+      'electronegativity out of range: ' + options.electronegativity );
 
     // @public (read-only)
     this.name = name;
diff --git a/js/common/view/PlateNode.js b/js/common/view/PlateNode.js
index eaafd131..dcd6daec 100644
--- a/js/common/view/PlateNode.js
+++ b/js/common/view/PlateNode.js
@@ -45,9 +45,9 @@ define( function( require ) {
     this.plateHeight = options.plateHeight; // @public used in view layout
 
     assert && assert ( options.polarity === 'negative' || options.polarity === 'positive' ,
-      'polarity must be "positive" or "negative"' );
+      'invalid polarity: ' + options.polarity );
     assert && assert ( options.perspective === 'right' || options.perspective === 'left' ,
-      'perspective must be either "left" or "right"' );
+      'invalid perspective: ' + options.perspective );
 
     Node.call( this );
 
diff --git a/js/common/view/PolarityIndicator.js b/js/common/view/PolarityIndicator.js
index ef14542f..f394134b 100644
--- a/js/common/view/PolarityIndicator.js
+++ b/js/common/view/PolarityIndicator.js
@@ -30,7 +30,7 @@ define( function( require ) {
     }, options );
 
     assert && assert ( options.polarity === 'negative' || options.polarity === 'positive' ,
-      'polarity must be "positive" or "negative"' );
+      'invalid polarity: ' + options.polarity );
 
     Node.call( this );