Understanding Electron Sub-Shells for AS Chemistry Exam

[Synkronised]

Firstly, hello everyone, I'm brand new to this forum

Anyway, I live in the UK, and in 3 days time I shall be taking my first AS level exam in Chemistry. The thing is, I still can't get my head around electron sub-shells; what they are etc etc.

Now, if anyone would be kind enough, can someone explain as simply as possible about them? I apologise if there is already a topic about this- please direct me there, but I'm getting pretty desperate now. I've spent the last week revising Biology (which i can do- hurray!), an our chemistry teachers are so bad...


Thankyou for any help, an happy new year to everyone.

-Synk-

 

[Chemicalsuperfreak]

What would you like to know? Each shell contain's one or more orbital (I don't like the term subshell). Each orbital contains two electrons. When you want to know which orbitals you'll be dealing with you just figure out how many electrons you have and us the Aufbau principle (just German for "building up").

You start with the 1s orbital, that's the only orbital in the first shell. It's spherical and like all orbitals and can hold two electrons.

If you've got more than two electrons you've got to go to the 2s orbital. This is spherical, all s orbitals are, and is slightly larger than the 1s orbital. If you've got more than four electrons you need to go up to the 2p orbitals.

There are 3 2p orbitals, each dumbell shaped and at right angles to each other. You need put one electron in at a time in each p orbital before putting two. So if you're dealing with nitrogen, which has seven electrons, you'll have two electrons in the 1s orbital, two electrons in the 2s orbital, and one electron in each 2p orbital. After you finish with 2p orbitals, you move up to the 3s orbitals, then the three 3p orbitals, and then the five 3d orbitals... after that it's kind of tricky, but there should be a list of which orbitals come after each other in your book, so make sure you study that.

 

[GCT]

The best way to think about them whollistically is to accept that the system (subshells, shells, pauli exclusion principle) exist the way it does due to the maximum stability within the confines of nature. It has evolved to its state.

Another way to become familar with it is to simply work on some problems. Read a review of the subject; I would recommend Schaum's Outlines for General Chemistry. You just need to learn the relationships between such terms as quantum numbers, shells, subshells, angular momentum etc... Practice, practice, practice. Remember that no two electrons in an atom can have the same four quantum numbers. Practice on problems which have to do with determining the quantum numbers of a specific electron (remember qn designate an electron within an atom). n, l, ml, ms
Be familiar with the above. I would suggest that you start from there.

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