Why does aballoon burts if you keep on blowing

The expansion is due to the elasticity of rubber. As we keep blowing, the air pressure builds up inside the balloon, and the rubber expands to its maximum limits. If we blow again, the balloon won't be able to expand but the air that we blows in need space still, and the balloon bursts.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8