The rate of the reaction is measurable quantity that refers to the amount or how much is are chemical substances reagents used up or converted into the product over some period of time.
Rate = change in the amount/time.
This can indirectly be observed through many ways, such as the volume of gas given off if the byproduct is a gas being produced, the colour of the solution etc.
The "sub shells" are the orientations and shapes for your orbitals, going in order by Shells are a collection of subshells with the same principle quantum number, and subshells are a collection of orbitals with the same principle quantum number and angular momentum quantum number. Hope this helps :)
n = m/M = 2/18 = 1/9 ~0,1 mol
States that the properties of elements are periodic or recurring and are correlated to their atomic number.
