In the following decay equation 24 11 Na is the......?

Oh, dude, you're hitting me with some science stuff now! Okay, so in the decay equation 24 11 Na, the 11 is the atomic number, telling us there are 11 protons in the nucleus of the sodium atom. The 24 is the mass number, which is the sum of protons and neutrons in the nucleus. So, like, that's what's going on there.