Out of the choices given, the part of the atom that forms chemical bonds are the outermost electrons. The correct answer is B.
Explanation:
(a) The given reaction equation is as follows.
(acidic)
So, here the reduction and oxidation-half reactions will be as follows.
Oxidation-half reaction: 
Reduction-half-reaction: 
As total charge present on reactant side is -1 and total charge present on product side is +3. And, since it is present in aqueous medium. Hence, we will balance the charge for this reaction equation as follows.
(acidic)
(b) The given reaction equation is as follows.
(basic)
So, here the reduction and oxidation-half reactions will be as follows.
Reduction-half reaction: 
Oxidation-half reaction: 
Hence, to balance the number of electrons in this equation we multiply it by 4 as follows.

Therefore, balancing the whole reaction equation in the basic medium as follows.
Answer: Fe2O3
Explanation: By applying crisscross method, the formula will be Fe2O3.
Answer:
physical change
Explanation:
the cutting doesnt change the chemical structure of the sodium