123 
want 
atom taking part. This is quite important as 1 
the energy evolved per atom in radioactivity. In the 1900*s it was re- 
cognized that the energy evolved per atom in the transmutation of ra- 
dium into radon, or indeed any radioactive element into another, was a 
than 
Radioac 
; thing. Chemical processes are very common. In 
that we see going on around us, combustion, cor- 
igetable metabolism and so forth, a chemicalpro- 
this is described in terms of the tangling or un- 
two 
volved . 
found 
energy evolve 
smaller than 
evolved per atom in radioactivity. This, among other things, led phy- 
sicists to the conclusion that radioactivity must be a property of the nu- 
lectrons 
of the atom. 
known as combustion 
control the evolution of heat at will. If you want more heat, you feed m 
more air to the furnace and if you want less, you diminish the air sup- 
ply. But there appeared to be no way whatever of controllmg the evolu 
tion of energy in radioactivity; it went on at its own pace and nothing 
pmiiH Hn wnniH «nppH it im or slow it down. It used to be said, 
that man 
that there is enough energy in a few ounces oi raaiu 
Ocean, but the catch is that 
would take 2000 years for the trip. So here was the tantalizing situation 
knew that there was a colossal amoxmt 
any 
a million times greater than is obtainable when the atom enters inio 
chemical combination. Yet whereas we had control of the evoluUon oi 
energy 
nucleus 
we did not need it. We had to wait vmtil 
release of nuclear energy 
this was effected only for one particular element, uranium, ^^^^^^^J^^ 
just exactly the right combination of properties to make it poss 
The study of radioactivity up to 1920 was rather like that oj astro -^ 
nomy. In a sense both are observational sciences for just as yo" 
go up in the sky and push the stars around to see how they w"J/ 
■ tions so you could do nothing to transmute one 
at°wUl. 1 1920, however, Rutherford -cceededm 
under 
another 
oxygen 
them with high energy alpha particles from radium. This was an I 
making discovery j t 
I have said that, in all ordinary processes that atoms undergo, i 
electron cloud shields their nuclei most effectively and so they J^" 
untouched. However, the alpha particles from radium ^re exceea i 
small but have tremendous energy --roughly 5 million volts a" 
enables them to crash 
alpha 
Indeed only one m 
