Which subatomic particle is the identity of the atom and why?

Asingle atom of an element has 21 neutrons, 20 electrons, and 20 protons. which element is it? ok o z

Consider the reaction of a(g) + b(g) + c(g) => d(g) for which the following data were obtained: experiment initial [a], mol/l initial [b], mol/l initial [c], mol/l initial rate, mol/l.s 1 0.0500 0.0500 0.0100 6.25 x 10^-3 2 0.100 0.0500 0.0100 2.50 x 10^-2 3 0.100 0.100 0.0100 1.00 x 10^-1 4 0.0500 0.0500 0.0200 6.25 x 10^-3 what is the rate law for the reaction?

How many grams of magnesium metal will react completely with 8.3 liters of 5.5m hcl? show all work