I think the correct answer is B. J.J. Thompson's Plum Pudding model had to be revised because atoms have protons and neutrons in the nucleus. He realized that aside from the electrons which are negatively charged, positive charge particles should be present to neutralize the charge of an atom.
Answer:
.
Explanation:
Consider the oxidation state on each of the element:
Left-hand side:
- O: -2 (as in most compounds);
- Cr:
; - Fe: +2 (from the charge of the ion);
Right-hand side:
Change in oxidation state:
- Each Cr atom: decreases by 3 (reduction).
- Each Fe atom: increases by 1 (oxidation).
Changes in oxidation states shall balance each other in redox reactions. Thus, for each Cr atom on the left-hand side, there need to be three Fe atoms.
Assume that the coefficient of the most complex species 
is 1. There will be two Cr atoms and hence six Fe atoms on the left-hand side. Additionally, there are going to be seven O atoms.
Atoms are conserved in chemical reactions. As a result, the right-hand side of this equation will contain
- two Cr atoms,
- six Fe atoms, and
- seven O atoms.
O atoms seldom appear among the products in acidic environments; they rapidly combine with 
ions to produce water 
. Seven O atoms will make seven water molecules. That's fourteen H atoms and hence fourteen ions on the product side of this equation. Hence the balanced equation. Double check to ensure that the charges on the ions also balance.
.
<u>Given:</u><u> </u>
Mass of Nitrogen (N₂) gas = 75 grams
<u>Finding the number of moles of N₂:</u><u> </u>
We know that the molar mass of N₂ is 28 grams/mole
Number of moles = Given mass / Molar mass
Number of moles = 75 / 28
Number of moles = 2.68 moles
Hence, there are 2.68 moles in 75 grams of Nitrogen Gas
Because it’s outermost ( actually , it’s only )
shell is full. The next shell holds 8 but it’s case it’s 2
