I am Using Dell Inspiron N5010. Can I Use Only Single Module 8GB RAM in Single Slot (With One Empty Slot)

The Inspiron™ N5010 / 15R system supports dual-channel DDR3 SDRAM with memory speeds of 1333 MHz

• Memory modules must be installed as a perfectly matched pair to take advantage of the dual-channel memory bus. If not a matched pair, the system's memory bus operates in a single-channel configuration. 

So yes you can use a single memory module but it will only run at single channel speeds. 

My information lists that the system is compatible with a 4096 GB memory module max, you may not be able to use an 8GB module. 

TB