The AtomType(String) constructor is updated so that only formal charg…

…e is set to 0 as indicated in the Javadocs. All other fields are set ot UNSET. Javadocs were updated to make this explicit

src/main/org/openscience/cdk/AtomType.java

@@ -102,18 +102,18 @@ public class AtomType extends Isotope implements IAtomType, Serializable, Clonea
     /**
      * String representing the identifier for this atom type with null as default.
      */
-    private String identifier;
+    private String identifier = (String) CDKConstants.UNSET;
 
     /**
-	 * Constructor for the AtomType object. Defaults to a zero formal charge.
+	 * Constructor for the AtomType object.
+     *
+     * Defaults to a zero formal charge. All
+     * other fields are set to {@link org.openscience.cdk.CDKConstants.UNSET}.
      *
      * @param elementSymbol  Symbol of the atom
 	 */
 	public AtomType(String elementSymbol) {
 		super(elementSymbol);
-		this.identifier = null;
-		this.formalNeighbourCount = 0;
-		this.electronValency = 0;
 		this.formalCharge = 0;
 	}