# Thread: Orbital, subshell and shell

1. Junior Member
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## Orbital, subshell and shell

hi everyone,

what are they? orbitals, shell, subshell......

thanks you

2. Senior Member
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## Re: Orbital, subshell and shell

Originally Posted by miracle
hi everyone,

what are they? orbitals, shell, subshell......

thanks you
These terms refer to the arrangement of electrons around an atom as determined through quantum mechanics.

First off, electrons are arranged by energy levels, or shells. These values are described by the principle quantum number n, with n being an integer greater than zero. These are equivalent to the stationary states in the Bohr model of the atom.

Within the shells, the electrons are organized into energy sublevels, or subshells. Within each energy level there are n subshells, described by the azimuthal quantum number l. l can have a value from 0 to (n-1). The value of l determines the shape of the subshell that the atom is in.

Sometimes you'll see the letters s, p, d, f... mentioned when talking about subshells. These letters are another way to write the value of the azimuthal quantum number. If l=0, s is used. If l=1, p is used. l=2, d is used, l=3, f is used. There are other letters for higher values of l.

So if we're talking about the subshell with n=2 and l=1, it can be written as the 2p subshell. The 2 tells us what the approximate energy of the electron within it is, and the p tells us more precise information about the energy of the electron, as well as telling us the shape of the volume the electron is generally found within.

The specific orbital is described by these two numbers as well as a third number, the magnetic quantum number ml. (The l should be a subscript, but I don't know how to do subscripts here). ml can take values from -l to +l, giving it 2l+1 total possibilities. Thus in any one energy level n, there is one s orbital; if n>1, there are three p orbitals, etc. Each orbital within a subshell is oriented differently than all the others.

Any general chemistry textbook should discuss these things in detail. It's all very confusing, I know. If you have any more questions about this (or anything else that has to do with chemistry) feel free to ask.

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