Quantum Numbers: Principal Quantum Number - Video Tutorials & Practice Problems
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The Principal Quantum Number gives both the size and energy of an electron shell.
Principal Quantum Number
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concept
Quantum Numbers: Principal Quantum Number
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2m
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The first quantum number of interest is the principal quantum number. It uses the variable n and the principal quantum number deals with the size of the shell, and the size of a shell is equal to the energy level of that shell. What we need to realize here is the value of for n increases, then both the size and energy level of an atomic orbital will also increase. Now, we're gonna say here that the energy levels or shell numbers of an atom can be tied to the periods or rows of the periodic table. So here we take a look at an atom, here we have our nucleus in the middle, we have here our first shell, so n equals 1, all the way to our 7th shell here which is n equals 7. These shell numbers are connected to the periods or rows of the periodic table. So shell 1 is connected to period 1. And as you can see, we went all the way up to to shell 7. And looking at the periodic table, we have periods 1 to 7. Now here's the thing, the periodic table, if you've watched my videos on it, we know that the periodic table is not a static thing, meaning that it's not gonna stay in this form forever. In fact, period 7, a lot of those elements in period 7 were only discovered within the past century. That's because as we explore new places on earth, as we explore the universe, as our technology becomes more advanced, we'll discover new elements, we'll create new elements. So theoretically, the number of rows in the periodic table is infinite. Right now we have 7 rows, but it can increase to 8 rows, 10 rows in a 1000 years. So just realize here that the number of rows for the periodic table doesn't stop at 7. It's only 7 now because of where we are technologically. In the future, there's gonna be more than 7 rows. So we're gonna find atoms that go beyond 7. This ties into the limitation of the principal quantum number. We're gonna say here that that the principal quantum number n must be an integer, so a whole number. And since it's connected to the periods of the periodic table, it has to start off at 1 at the lowest as its lowest possible value. And we just said that the number of rows is not static, it increases over time. So n theoretically can be any whole number from 1 to infinity. So just realize that on an exam or a quiz you see n equals 22, that's possible. We just haven't gotten there yet. So just remember, the principal quantum number is connected to the size and energy of a shell and it affects the size and energy of the orbitals.
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example
Quantum Numbers: Principal Quantum Number Example 1
Video duration:
56s
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Here in this example question, it says, which of the following is a possible value for a principal quantum number shell? So here we have n equals negative 3, negative 4, 0, 11, and negative 7. Remember, we said that your principal quantum number n is connected to the periods or rows of the 7 rows, but in the 7 rows, but in the future, we're gonna we're gonna have 8, 9, 10 rows. It can continue onward. So here, theoretically, n equals any value from 1 to infinity. That means all these negative values would not work, and n cannot equal 0. Has to start off as 1 as a possible value. So the answer here would have to be option d. Theoretically, n can equal 11.
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Problem
Problem
What is the value of n for the electron based on the image of the atom provided?
A
n = 3
B
n = 5
C
n = 1
D
n = 2
E
n = 6
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Problem
Problem
Which electron possesses the lowest possible energy from the image provided?