# orbital arrangement

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hye ! one of my friend asked me about arrangement of orbitals in an atom i.e how 1s, 2s, 2p, 3s, 3p, 3d............... orbitals spaced in an atom ? please suggest me the app. ans .

thanks

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It's been sooo.. long since I done this. Don't the 4s ones fill up after the 3d ones are only half full? They sort of give a stable half shell then the 4s levels start to fill as a full 4s shell is more stable than 3d shell with 6 or 7 electrons.

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your question seems to be asking how the orbitals are arranged spatially compared to each other. The answer is that they're all arranged on top of each other, which is why they're usually drawn separately, since the drawing would look a bit messy if you drew them all on top of each other.

it's possible you meant how are they arranged in terms of their relative shapes, in which case klaynos's answer is correct.

Dr P i'm afraid you're wrong, the 4s ones fill up first, then there's a point where the 4s gives up an electron in order to allow Cr to have a half full 3d, then it fills up again for Mn, then again the 4s gives up an electron to allow Cu to have a full 3d and fills up again for Zn. After the first row of transition everything goes normally until you reach the second row where things start to get confusing. After that exception start to become the rule and we give up trying to teach it.

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OK - thanks - knew it was something along those lines. Thus, why I worded it without much confidence as a question rather than a statement of fact. I hope it came accross like that.
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2s has one node , 3s has two node and so on . what are these nodes ? and where are these nodes in an atom ?

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a node is a region of space where the probability of finding an electron is zero. There are two types of node. Angular and radial. A radial node is spherical in shape, whereas angular nodes are planar or conical. the total number of nodes in an orbital is equal to n-1, where n is the principle quantum number.

In the examples you gave, 2s has one radial node. You can't see it unless you do a diagram with a cut-away, since the orbital is basically a sphere inside a sphere. The 3s orbital has another layer on the outside of that.

My avatar is an orbital which isn't usually occupied, I cant remember which, but you can see it has several (i counted 4) radial nodes, and two conical angular nodes.

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I am sure in most text books about inorganic chemistry they give a mnemonic which will help the OP to remember which sub-shell is filled first. As per why one orbital is filled first compared to the other the answer is simply low energy orbitals are filled first.

hope that help OP a bit.

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there's no need for a mnemonic. They're filled according to the n+l rule, sometimes known as the madelung rule. I've never seen it in a textbook but i always teach it to my students. It works.

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there's no need for a mnemonic. They're filled according to the n+l rule, sometimes known as the madelung rule. I've never seen it in a textbook but i always teach it to my students. It works.

Fair enough then, I was only trying to help the OP though !

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here's a useful link. I downloaded the software used to draw these orbitals and it really helped me understand them better. I even made the four sp3 hybrid orbitals
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ya this link is a complete link between my ques. and ans. thanks

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Hi,

Realise this is a slight bump, but...

there's no need for a mnemonic. They're filled according to the n+l rule, sometimes known as the madelung rule. I've never seen it in a textbook but i always teach it to my students. It works.

Is this not the same as the Aufbau principle? If so it's in most modern books.

Kaeroll

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the aufbau principle is a little less detailed than the n+l rule. The aufbau principle is usually only taught up to an including the 4p elements, since after that it gets a bit confusing. Also it's only taught that the 4s elements come before the 3d, but not why, whereas the n+l rule is a simple way of deciding which subshell to fill up next all the way through the periodic table. It still doesn't cover the exceptions like copper and chromium, though.

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Fair enough - I guess I've always used the n+l rule under the wrong name! Cheers for the clarification.

Kaeroll

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1s - 1

2s - 2

2p - 3

3s - 3

3p - 4

4s - 4

3d - 5

4p - 5

5s - 5

4d - 6

5p - 6

6s - 6

4f - 7

5d - 7

6p - 7

7s - 7

6d - 8

now we are got same n+l values for some orbitals , which is going to filled first ?

so i feel Aufbau is the most general one .

Edited by vedmecum
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the n+l rule isn't just which one has the lowest n+l value. the addendum is that the one with the lowest value of n will go first in case of a draw. The rule is also known as the madelung rule. These aren't really two conflicting rules... the n+l rule is the important part of the aufbau principle. The annoying thing is that mostly students are taught which order the subshells are filled but not WHY.

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the n+l rule isn't just which one has the lowest n+l value. the addendum is that the one with the lowest value of n will go first in case of a draw. The rule is also known as the madelung rule. These aren't really two conflicting rules... the n+l rule is the important part of the aufbau principle. The annoying thing is that mostly students are taught which order the subshells are filled but not WHY.

I know when I was taught this in the first year as an ug, I was given a vague "lower energy". Great for the most part, but not so clear once you reach the d block.

Kaeroll

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I know. I think teaching the n+l rule wouldn't be a bad idea. It still doesn't cover the exceptions, but it does explain the shape of the periodic table perfectly.

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