A LEVEL CHEMISTRY!! Please Help?

Question

What does it mean when it says the 3S sub-shell is filling. Its in the CGP A level Chemistyr book but it doesnt explain what it means. Also why do electrons have to spin pair. Thanks

Answer 1

The basic idea of orbitals to explain how electrons are arranged and paired inside of an atom. The bigger the element the more numbers of subshells/orbitals you will see from an atom. The main subshells that people often work with are S,P,D,F. The S subshell can only hold 2 electrons because it has one orbital, that is the maximum number of electrons an orbital could hold. Because the S subshell can hold two electrons, if it has two electrons then it is full/ filling. So if there is one electron what can you say about the S orbital?

In a orbital the two electrons are not allowed to spin in the same direction, so that is why you have a positive spin and negative spin.

If it helps look up the Aufbauf principle in your book or online for a more detailed explaination.

Answer 2

electrons have shells that are filled in an ascending manner.

It goes 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p and so on

These shells are filled in sequence. Each shell has subshell which can only hold a max of 2 electrons

An s shell has 1 subshell and can hold 2 e

p has 3 subshells and can hold 6e

d has 5 subshells and can hold 10 e.

It is something you have to memorize for doing electronic configuration.

You probably would want to have a look at this website

http://www.iun.edu/~cpanhd/C101webnotes/...

Now why do electrons have a spin pair. Because a subshell contains only 1 electron, it tends to be a little unstable and willing to lose that e. If there are 2 electrons, they spin in opposite directions and cancel out the effect.

Half filling means a subshell has 1 e so its half filled

Hope tht clarifies everything