The Electron Configuration Review - Video Tutorials & Practice Problems
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concept
Ground State Electron Configurations
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When writing the electron configuration of an element, it's important that it represents the distribution of electrons from 1 s to 2 s to 2 p and so on within orbitals using the Aufbau principle. Now with the Aufbau principle it says, starting with 1 s, we're going to have electrons filling lower energy orbitals before moving on to higher energy orbitals. We begin with 1 s when we're doing the the full ground state electron configuration of an element or an ion. To help us with this, you could take the Aufbau diagram approach. We start out with 1 s, then we move on, loop back around to 2 s, then we loop back around to 2p, then to 3s, then we loop back around to 3p, and then 4s, then continuously loop back around to 3d, to 4p, to 5 s. Now, this is our off ball diagram. In the off ball diagram we have here one s all the way down to 8 s. Then we have 2p to 3 to 7p. Then we have 3d to 6 d, and then we have 4 f and 5 f. Another way we can look at determining the electron configuration has to do more with the periodic table. So if you click on the next video, let's reimagine what the periodic table will look like when dealing with the electron configuration of elements and ion.
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concept
Auf Bau Principle
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So here if we reimagine the periodic table, we'll see it in this depiction. Now realize here we have blue, we have yellow, we have purple, and we have red sectors. Now each of these is called a block s. The s block is what's in blue, this is the p block, the d block, and the f block. Remember the s sublevel has 1 orbital and that one orbital can hold a maximum of 2 electrons, which is why the s block is these 2 columns, to represent the 2 maximum electrons that the s sublevel can hold. The p sublevel has 3 orbitals, right, and each one again can hold a maximum of 2 electrons. So p theoretically can hold a maximum of 6 electrons. That's why the p block has 1, 2, 3, 4, 5, and 6 slots for it. D can have up to 10 electrons because it has 5 orbitals, and if you count you'll see in here there's 10 spots. And then for the f sub levels, they can hold up to 14 electrons, and if you were to count these rows in red you'd see they come out to 14. Now, realize here that in this periodic table the first slot here, which represents hydrogen, starts off our electron configuration as 1 s 1. Then as we move to the next one we add another electron, electron, so helium is 1 s 2. Then when we get to the 2nd row, since we're in the 2nd row, we now have 2. This is still the s block, so this is 1 s 2, 2 s 1, and it continues onward and onward. Over here we'd go 1 s 2, 2 s 2, 2 p 1. So following this pattern this would be 3 s, 4 s, 5 s, 6 s, and 7s. And then here this would be 3p4p, 5p, 6p, and 7p. When we go to the d block, realize that it's gonna drop down by 1. So here this is 4 s, but then when we go to d block, it drops down by one number, so now it's 3 d. This would be 4 d, 5 d, and 6 d. Now, notice how this number goes from 57 to 72, that's because 58 to 71 are here. Remember this this red line here says that this entire red row exists in between 57 and 72. And then we go between 89 and 104 because 90 to 103 is down here. These are your f blocks. They also drop down by one number. So this is 4 f and 5 f. So basically, if you can reimagine the periodic table in this fashion, you can use it to figure out the electron configuration of any element or ion given to you. So we're gonna put this periodic table to use in order to do future electron configurations.
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example
The Electron Configuration Example
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To help us with this example question, I decided to leave this periodic table up so we can see how to best use it. Here it says write the ground state electron configuration for the following element. Here we're dealing with fluorine, and they tell us that it has an atomic number of 9, which means it has 9 electrons. On this periodic table, we find fluorine right here. Ground state means that we're gonna start out with 1 s orbital and work our way up to fluorine. So we're gonna count to fluorine. So we'd say 1 s 2, 1 s 2, 2 s 2 because of 1, 2 slots. And then we have to count to f, so that would be 2 p, we're in the 2 p row. And how many slots do we have to count to to get to fluorine? 1, 2, 3, 4, 5. 2p5. So here, this would be the ground state electron configuration of the Fluorine atom. And realize here that these are the number of electrons. So when you add them up, 2+2+5, that gives me 9 electrons, which is related to the atomic number here of Fluorine. Remember, when an element is neutral, its atomic number tells us both the number of protons and the number of electrons. So again, rely on this depiction of the periodic table to help guide you to the right electron configuration of any element or ion given to you.
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Problem
Problem
Which electron configuration represents a violation of the Auf Bau Principle?
A
B
C
D
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Problem
Problem
Identify the element with the given electron orbital diagram.
A
Silicon
B
Fluorine
C
Sulfur
D
Chlorine
E
Phosphorus
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Problem
Problem
Write the electron configuration and electron orbital diagram for the following element:
Mn (Z = 25)
A
1s2 2s2 2p6 3s2 3p6 4s2 3d5
B
1s2 2s2 2p6 3s2 3p6 4s2 4d5
C
1s2 2s2 2p6 3s2 3p6 4s2 3d4
D
1s2 2s2 2p6 3s2 3p6 4s2 3d5
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Problem
Problem
Write the ground-state electron configuration for the following element:
We're going to say here that the condensed electron configuration is a faster way to write out electron arrangements for elements or ions. We're going to say with condensed electron configurations, we start at the last noble gas before the desired element. And if we take a look here, remember, this is our reimagining of the periodic table. We have our s Bloch where it begins with 1 s. Have our p block here, we have our d block here, and we have our f block down here. With the condensed electron configuration, it's important to know which element are we being asked to find the electron configuration of, and what's the noble gas before it. Unless they say full ground state electron configuration, we usually just assume that this is the method they want us to write the electron configuration. So now that we know what the condensed electron configuration is, click on the next video, and let's get to work on an example question.
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example
The Electron Configuration: Condensed Example
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Here it says to provide the condensed electron configuration for the aluminum atom. Atom means that we're dealing with the neutral form of it. If you look on the periodic table, so step 1, we have to find the element on the periodic table. So aluminum has an atomic number of 13, which means it has 13 electrons involved. Step 2, we're gonna locate the noble gas that comes before the element and place it inside brackets. So the noble gas before aluminum is neon, so put it in brackets. Step 3, continuing from the noble gas in brackets complete the rest of the electron configuration. So we dealt with neon, so let's continue onward to aluminum. So next would come 3 s 2, and then 3p1. So this would be the condensed electron configuration of aluminum. Instead of having to write 1 s 2, 2 s 2, 2p6, 3 s 2, 3p 1, we have this new condensed electron configuration. Neon here is taking the spot of all of this. So it's easier and faster for us to write the electron configuration of aluminum in this regard. So just remember, the condensed electron configuration saves us a lot of time in terms of writing out the electron arrangements for elements and ions.
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Problem
Problem
Write the condensed electron configuration and electron orbital diagram for the following element: Zinc