Hi Fateme,
I originally hoped to use the workflow to trigger the pop up when validating notes created containing 'chat' which seems be more higher performance. While I demoed&found it's couldn't be completed to trigger web resource/JS from Workflow.
Since I would suggest you to write an onLoad script to retrieve the value of the notes whether it contains the request for chat and then show window's alert to realize the pop up window .
Some similar ticket could be for your reference:
community.dynamics.com/.../204304
Hope the above info could help.
Regards
Johnny