can you use the first gen Apple Pencil for the new iPad Air?

No. Only the second generation Apple Pencil can be used with the 2020 iPad Air4.

Here is the full compatibility list for Apple Pencil and iPad:

Apple Pencil (2nd generation)

You can use Apple Pencil (2nd generation) with these iPad models: 

• iPad Air (4th generation)
• iPad Pro 12.9-inch (3rd generation) and later
• iPad Pro 11-inch (1st generation) and later

Apple Pencil (1st generation)

You can use Apple Pencil (1st generation) with these iPad models:

• iPad (8th generation)
• iPad mini (5th generation)
• iPad (7th generation)
• iPad (6th generation)
• iPad Air (3rd generation)
• iPad Pro 12.9-inch (1st or 2nd generation)
• iPad Pro 10.5-inch
• iPad Pro 9.7-inch

Not sure which iPad you have? Identify your iPad model.

NO.

You absolutely need to purchase and use the newest 2nd gen Apple Pencil.