public void SetWidth( 
   double width
)

//Modify an element's width.

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  double elmWidth = element.GetWidth();
  elmWidth = 8.5;

  element.SetWidth(elmWidth); //You don't have to get to set; a shortcut would be: element.SetWidth(8.5);
});

//Create a scale bar for a specific map frame and assign a scale bar style item.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Reference a North Arrow in a style
  StyleProjectItem stylePrjItm = Project.Current.GetItems<StyleProjectItem>().FirstOrDefault(item => item.Name == "ArcGIS 2D");
  ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars("Double Alternating Scale Bar 1")[0];

  //Build geometry
  Coordinate2D center = new Coordinate2D(7, 8);

  //Reference MF, create north arrow and add to layout 
  MapFrame mf = layout.FindElement("New Map Frame") as MapFrame;
  if (mf == null)
  {
    ArcGIS.Desktop.Framework.Dialogs.MessageBox.Show("Map frame not found", "WARNING");
    return;
  }

  //At 2.x -
  //ScaleBar sbElm = LayoutElementFactory.Instance.CreateScaleBar(layout, center, mf, sbStyleItm);
  //sbElm.SetName("New Scale Bar");
  //sbElm.SetWidth(2);
  //sbElm.SetX(6);
  //sbElm.SetY(7.5); 

  var sbInfo = new ScaleBarInfo()
  {
    MapFrameName = mf.Name,
    ScaleBarStyleItem = sbStyleItm
  };
  var sbElm = ElementFactory.Instance.CreateMapSurroundElement(
                                      layout, center.ToMapPoint(), sbInfo, "New Scale Bar") as ScaleBar;
  sbElm.SetWidth(2);
  sbElm.SetX(6);
  sbElm.SetY(7.5);
});