There is no such thing as an iPad Air 8th Gen. The current model of iPad Air is the 4th Generation.The current model of the regular iPad is the 8th Generation. They are 2 different iPads.
Please identify the exact type of iPad you have as Apple Pencil compatibility is different between the 2. link->Identify your iPad model - Apple Support
The second generation Apple Pencil works and can be charged with the iPad Air 4th generation if that is what you have, It will not work, and cannot be charged with the iPad 8th generation.
The second generation Apple Pencil attaches to the side of the iPad Air to charge and pair.
See here: link->Apple Pencil compatibility - Apple Support
and here: link-> Connect Apple Pencil with your iPad - Apple Support