Answer : Option 1) nuclei of
and nuclei of
only.
Explanation : Radiation is spontaneously emitted from nuclei of
because this isotope of hydrogen is highly radioactive as compared to other isotopes of hydrogen namely; nuclei of
and nuclei of
.
They have much stable nucleus as compared to nuclei of
.
The more it is unstable the more radiations will be emitted from its nucleus.
Once you balance the enquation you "switch partners" of the element (negative charge to positive charge)
the answer is: Atomic number
Aluminum is light and is quite unreactive it is malleable and strong too.