A pair of AirPods weighs the same as two ordinary plastic bags, the grocery store kind.

Lithium? About a gram of lithium in a disposable AA lithium battery. About 0.015 grams per AirPod proper, and another 0.16 grams in the case. So call it 0.2 grams, or when you toss five (5) AirPods with their cases, that's as much lithium as one (1) disposable AA battery.