Modern gas & electric ovens both "click" at times.  

Normal Oven Sounds

Electric ovens will make a clicking sound more often compared to gas.  

The reason is that electronically controlled ovens use "relays" to cycle the heater on and off.  These "relays" making a clicking sound each time this happens.

While the oven is cooking and up to 1 hour after intermittent clicking may be totally normal operation.