diff --git a/js/common/view/BANScreenView.ts b/js/common/view/BANScreenView.ts
index 9e78155..b2e7886 100644
--- a/js/common/view/BANScreenView.ts
+++ b/js/common/view/BANScreenView.ts
@@ -192,7 +192,7 @@ abstract class BANScreenView<M extends BANModel<ParticleAtom | ParticleNucleus>>
       if ( particleType === ParticleType.PROTON || particleType === ParticleType.NEUTRON ) {
 
         // called when a nucleon is finished being dragged
-        particle.dragEndedEmitter.addListener( () => { this.dragEndedListener( particle, this.model.particleAtom ); } );
+        particle.dragEndedEmitter.addListener( () => this.dragEndedListener( particle, this.model.particleAtom ) );
         this.checkIfCreatorNodeShouldBeInvisible( particleType );
       }
 
diff --git a/js/common/view/NucleonArrowButtons.ts b/js/common/view/NucleonArrowButtons.ts
index 99a0e0f..ca411c2 100644
--- a/js/common/view/NucleonArrowButtons.ts
+++ b/js/common/view/NucleonArrowButtons.ts
@@ -65,11 +65,11 @@ class NucleonArrowButtons extends Node {
         const neutronNumber = atomNeutronNumber + incomingNeutronsNumber + userControlledNeutronNumber;
         const userControlledNucleonNumber = userControlledNeutronNumber + userControlledProtonNumber;
         const doesNuclideExist = AtomIdentifier.doesExist( protonNumber, neutronNumber );
+        const massNumber = atomProtonNumber + atomNeutronNumber;
 
         // Disable all buttons if the nuclide doesn't exist and one of the two cases:
         // Something is being user controlled OR Particle Atom is not empty
-        if ( !doesNuclideExist &&
-             ( model.particleAtom.massNumberProperty.value !== 0 || userControlledNucleonNumber !== 0 ) ) {
+        if ( !doesNuclideExist && ( massNumber !== 0 || userControlledNucleonNumber !== 0 ) ) {
 
           // disable all arrow buttons if the nuclide does not exist
           NucleonArrowButtons.toggleCreatorNodeEnabled( protonsCreatorNode, false );