Answer: 5
Explanation: Arsenic, As, has 5 electrons in the 4th energy shell. 4s^2 and 4p^3. The electrons being added for the elements scandium through zinc are all going into the 3d orbital, in the 3rd energy shell. They don't count, since valence electrons are only those in the highest energy level, 4 in this case.
Because it may not contain Hydrogen or Oxygen
Iron (II) Acetate : Fe(C2H3O2)2
The chain reaction is easy to stop. Just add a neuron absorbing material. The Control Rods in rectors can do that You just SCRAM (put the rods all the way in) or add something like Boron and the chain reaction stops.
<span>The problem is the radioactive waste. Those isotopes break down and release heat spontaneously, no neutrons required. The only known way to stop or slow radioactive decay down is to slow time down by moving at relativistic speed or near orbit to a black hole.</span>
The solutions are the following :
12. C
13. A.
