It is 2.1 x 10^3 because your base number needs to be in between 1 and 10, and the number you are converting is non-decimal, so the exponent is positive. It is 10^3 because you are moving the decimal 3 places to the right
For Nitrogen Atom:
Atomic Number - 7
Protons - 7
Neutrons - 8
Electrons - 7
Cation/Anion - Anion
For Nitrogen Ion:
Atomic Number - 7
Protons - 7
Neutrons - 8
Electrons - 10
Atomic Symbol - N3-
**Visible confusion** no problem
Answer:
B. 
Explanation:
The unit for rate is M/s while the unit for each molecule should be M. You can find the unit for k by putting the units for rate and the molecules into the equation
rate= k{X][Y]
M/s= k *
* 
k= (M/s) / (
)
k= 
You can also use this predetermined formula to solve this problem faster: k= 
Where n is the number of molecule. There are 3 molecule(2X and 1Y) so n=3, so
k= 
k=
=
= 