The nucleus of an atom of cobalt-58 contains(1) 27 protons and 31 neutrons(2) 27 protons and 32 neutrons(3) 59 protons and 60 neutrons(4) 60 protons and 60 neutrons

The number next to cobalt (58) represents the atomic mass.
The atomic mass consists of protons and neutrons.
We know that the atomic number = # of protons.
 
- Look at a periodic table to find Cobalt's atomic number which is 27, meaning there are 27 protons.
-To find the number of neutrons, take 58-27 = 31 neutrons.

Therefore the answer is (1) 27 Protons and 31 Neutrons

The gas would begin to expand, and eventually the can would burst or explode.