10. Periodic Properties of the Elements

# The Electron Configuration: Quantum Numbers

The **Quantum Numbers** ultimately can be used to determine the precise location of an electron.

Electron Configuration & Quantum Numbers

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concept

## The Electron Configuration: Quantum Numbers

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in order to relate the quantum numbers to an electron configuration, it's first important to know how to number the electrons within an electron orbital diagram. We're going to say here that electrons within configurations are numbered in the order. They're written based on the off about principle. Remember, with the off about principle, we start out with one s orbital and we move onward. So one s in two s than two p, and so on. Knowing this order is the key to numbering the electrons correctly and from there will be able to link the quantum numbers to them.

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## The Electron Configuration: Quantum Numbers Example 1

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here. We need to determine the number of the electron highlighted within the electron orbital diagram. So if we look, this is what one has to to us too. Two p six three s to three p four and we're looking at this electron here. We have to determine its number. Alright, so we number it in the order off the off ball principle. So we start out with one s too. So we start numbering them first. So one up. So 11 down to one up. Three one down. Four now two p. These are degenerate orbital's. They have the same energy. So following Hunt's role, we have build them first. So this would be up, up, up. So I number them 567 Then we came back around 89 10. Now we're at three us again. So 11. 12 three p Orbital's there, degenerate. Same energy again. So half fill according to Hunt's role. 13, 14, 15, 16. And we can see here that this electron that's highlighted is the 14th electron. So remember, that's the way we're able to number the electrons within an electron orbital diagram. This is key for lady later on, connecting it to the quantum numbers

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concept

## The Electron Configuration: Quantum Numbers

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So here we're gonna have a quick review of the quantum numbers. So we're going to say, Remember, the quantum numbers are set of values that described the energy levels and ultimately the location of a specific electron. Now here, with our principal quantum number, our first one, it's variable is end. It describes the size and energy of a shell. So, for example, let's say we're dealing with a set of seven D orbital's because the number is seven. That means we're dealing with electrons in the seventh shot and therefore an equal seven. The angular momentum quantum number, also called the as a mutual quantum number, uses the variable L. It gives us the shape of an orbital within a sub shop here. Sub shells are sub levels. They are represented by the letters of S P D N F. If you know the sub level or sexual letter, then you know what your L value is. S zero p is one ds two and l s three. I mean, if it's three, the magnetic quantum number deals with the variable m sub l. It gives us the location of electrons within a set of orbital's. So for example, let's say we're dealing again with seven d orbital's. Remember that your deep sub level has five orbital's involved. Each of those orbital's has a number designation. So here this would be negative to negative 10 plus one and plus two. So those numbers are the possible values. They are the numerical location of each of these orbital's, and within each of those orbital's, we have electrons. Finally, we have our spin quantum number, which is M CBS. It gives us the spin of an electron within an orbital. Remember, an orbital can hold a maximum of two electrons, one spins up and would have on M s or n sub X value of plus one half the other one spends down and would have an M s value of negative one half. So this is a crash course in quantum numbers. If you didn't get a chance to look at my earlier videos, if you haven't, I highly suggest you go back and take a look. Quantum numbers could be a bit tricky, so it's important to understand these fundamental ideas on how they relate the ultimate location of an electron within a given. Adam

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example

## The Electron Configuration: Quantum Numbers Example 2

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here, it says, Give the set off four quantum numbers for the sixth electron of the oxygen atom. So here it says, provide the electron orbital diagram for the elements or ion. Alright, So oxygen atom means oxygen is neutral. Oxygen has an atomic number of six. Here it's electron configuration. Would be one s two to ask to to p four filling in this electron orbital diagram, one has to so one up one down to us to one up, one down. The next four electrons are found within our two p set of orbital's. Since they're all two p electrons, they all have the same energy. So following hunts rule we have Phil first up, up, up And here is my seventh on my fourth electron. So now step to use the number and letters for the set of orbital's to determine its n and l values. All right, so we're looking for the sixth electron. So this is one to 34 half filled 1st 567 and then back around eight. Sore six electron is right here. What? All right, so we're going to say here that that electron that we're looking at it is within a two p set of orbital's because the number is two and equals two. Because the letter is P, that means l equals one. Remember, if you know the sub level letter, then you know what Ellis. So if it's pl is one next, locate the specific orbital for the electron to determine its M sub l value. The electron we're looking at is in the zero orbital that is equal to the possible and then finally determine if the electron spins up or spins down to determine the subs value. It is pointing up. That means M sebas equals plus one half. So the four quantum numbers for the sixth electron with an oxygen would be an equals to l equals one. M. Sobel equals zero and M subs equals plus one half. But remember, we can't do this unless we're able to correctly number the electrons as they appear within the electron orbital diagram.

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Problem

Give the set of four quantum numbers that represent the indicated electron in each of the following elements.

Mg (7th electron)

A

n = 2; l = 2; ml = 0; ms = +1/2

B

n = 2; l = 1; ml = 0; ms = -1/2

C

n = 2; l = 1; ml = +1; ms = +1/2

D

n = 2; l = 1; ml = +1; ms = -1/2

E

n = 2; l = 1; ml = -1; ms = +1/2

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Problem

Give the set of four quantum numbers that represent the indicated electron in each of the following elements.

Cl^{–} (18th electron)

A

n = 3; l = 0; ml = +1; ms = -1/2

B

n = 3; l = 0; ml = -1; ms = -1/2

C

n = 3; l = 2; ml = +1; ms = -1/2

D

n = 3; l = 1; ml = +1; ms = +1/2

E

n = 3; l = 1; ml = +1; ms = -1/2

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Problem

Give the set of four quantum numbers that represent the indicated electron in each of the following elements.

Cr^{3+} (21^{st }electron)

A

n = 3; l = 1; ml = 0; ms = -1/2

B

n = 3; l = 2; ml = 1; ms = -1/2

C

n = 3; l = 1; ml = 1; ms = +1/2

D

n = 3; l = 2; ml = 0; ms = +1/2

E

n = 3; l = 1; ml = 0; ms = +1/2

Additional resources for The Electron Configuration: Quantum Numbers

PRACTICE PROBLEMS AND ACTIVITIES (13)

- Use the periodic table to determine each quantity. a. the number of 2s electrons in Li
- Use the periodic table to determine each quantity. c. the number of 4p electrons in Br
- Use the periodic table to determine each quantity. b. the number of 3d electrons in Cu
- Use the periodic table to determine each quantity. a. the number of 3s electrons in Mg b. the number of 3d ele...
- Assign a set of four quantum numbers for the outermost two electrons in Sr.
- Why does the number of elements in successive periods of the periodic table increase by the progression 2, 8, ...
- Iron is commonly found as Fe, Fe2+, and Fe3+. (b) What are the n and l quantum numbers of the electron removed...
- You have cracked a secret code that uses elemental symbols to spell words. The code uses numbers to designate ...
- (f) Can contain two electrons, both with spin ms = +1/2
- (b) Can have ml = -1
- Given the subshells 1s, 2s, 2p, 3s, 3p and 3d, identify those that meet the following descriptions. (a) Has l ...
- (c) Draw an orbital-filling diagram for the element with atomic number 12.
- Assume that the rules for quantum numbers are different and that the spin quantum number ms can have any of th...