According to the scatter chart properties documentation, use markerShapePalette which has options shown under the shape and shape palette documentation. Neither circles nor bubbles are options.
You can, however, change the chart type to bubble and get what you want. For details, go to the bubble chart properties documentation.
Hi @jtrucks , yes I had gone through the documentation before. there they have mentioned the shape as bubble for bubble chart only. i even tried using the code for scatter chart also but didnt worked. any ideas @jtrucks