Millions of fission reactions occurring one after the other because of the bombardment of neutrons into atoms with a release of energy is called
a chain reaction.
radioactive sublimination.
natural transmutation,

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

i think its 100.

hope this !