Electrons have places around the atom that they are most likely to be. An electron configuration is a way of describing these places, like an address for electrons. Each part of what you just wrote out describes a place where electrons can be found in oxygen. Let\'s take a look at just the first part: 1s2. The \'1\' is the shell. The shell number is used to indicate how close to the nucleus the electrons are. The first shell is the *closest* possible spot for the electrons - the higher this number becomes, the farther away from the nucleus they go. The \'1\' shell MUST be get its electrons before the \'2\' shell or \'3\' shell, and so on - it gets priority. With me so far? :) The \'s\' is the subshell, which refers to the SHAPE of the area where the electron might be. \'S\' stands for \'spherical\', like a beach ball. Imagine a sphere like that around the nucleus - electrons in the 1s area can be anywhere on that shell. Finally, we\'ve got the \'2\' of 1s2. This indicates the number of electrons present. ALL \'S\' SHELLS CAN HOLD NO MORE THAN 2 ELECTRONS. EVER. So when you get to 2s? It should have 2 electrons as well, when it\'s full. 3s? Should also have two electrons. ANYTHING with an \'s\' should have up to two. So, the fact that 1s comes before 2s comes before 2p? That must be memorized, unfortunately. There is a handy chart to help you remember the correct order; you can find it here: http://education.jlab.org/qa/electron_config.html. Now we come onto how you do an electron configuration for a specific atom. Let\'s say your teacher tells you to draw the electron configuration for oxygen. You look on the Periodic Table (go ahead) and see that the number of electrons in an oxygen atom is eight. Now your job is to use this code we\'ve talked about to describe where each of those eight electrons is in an oxygen atom. You have to start putting electrons in the \'1\' shell because you always fill the \'lowest\' (closest to the nucleus) level first. So you have 1s2, two electrons in the first shell, darting around over a sphere. That means you have two electrons so far. But oxygen has eight all together - the PT says so. So we keep going. Again with the memorization, we know that 2s is next, and all \'s\' subshells have up to two electrons. So we now have 1s2, 2s2. That\'s still only four electrons all together. We have to keep going. Next is 2p. \'p\' subshells can hold up to six electrons. BUT, if we do six... 1s2, 2s2, 2p6... adding up our electrons gives us 10. Oxygen only needs eight electrons! So we need: 1s2, 2s2, 2p4. Now we have 8 electrons all together. ALL atoms are done in exactly the same way. You figure out how many electrons they have, then keep going with the electron configuration \'addresses\' until you have reached the right number of electrons (and remember - the number of electrons is represented by the number AFTER the letter; not before). Try these: Do the electron configuration for helium and neon and chlorine using the.

1. Electrons have places around the atom that they are most likely to be. An electron configuration
is a way of describing these places, like an address for electrons. Each part of what you just
wrote out describes a place where electrons can be found in oxygen.
Let's take a look at just the first part: 1s2.
The '1' is the shell. The shell number is used to indicate how close to the nucleus the electrons
are. The first shell is the *closest* possible spot for the electrons - the higher this number
becomes, the farther away from the nucleus they go. The '1' shell MUST be get its electrons
before the '2' shell or '3' shell, and so on - it gets priority. With me so far? :)
The 's' is the subshell, which refers to the SHAPE of the area where the electron might be. 'S'
stands for 'spherical', like a beach ball. Imagine a sphere like that around the nucleus - electrons
in the 1s area can be anywhere on that shell.
Finally, we've got the '2' of 1s2. This indicates the number of electrons present. ALL 'S'
SHELLS CAN HOLD NO MORE THAN 2 ELECTRONS. EVER. So when you get to 2s? It
should have 2 electrons as well, when it's full. 3s? Should also have two electrons. ANYTHING
with an 's' should have up to two.
So, the fact that 1s comes before 2s comes before 2p? That must be memorized, unfortunately.
There is a handy chart to help you remember the correct order; you can find it here:
http://education.jlab.org/qa/electron_config.html.
Now we come onto how you do an electron configuration for a specific atom. Let's say your
teacher tells you to draw the electron configuration for oxygen. You look on the Periodic Table
(go ahead) and see that the number of electrons in an oxygen atom is eight. Now your job is to
use this code we've talked about to describe where each of those eight electrons is in an oxygen
atom.
You have to start putting electrons in the '1' shell because you always fill the 'lowest' (closest
to the nucleus) level first. So you have 1s2, two electrons in the first shell, darting around over a
sphere. That means you have two electrons so far. But oxygen has eight all together - the PT says
so. So we keep going. Again with the memorization, we know that 2s is next, and all 's'
subshells have up to two electrons. So we now have 1s2, 2s2. That's still only four electrons all

2. together. We have to keep going.
Next is 2p. 'p' subshells can hold up to six electrons. BUT, if we do six... 1s2, 2s2, 2p6...
adding up our electrons gives us 10. Oxygen only needs eight electrons! So we need: 1s2, 2s2,
2p4. Now we have 8 electrons all together.
ALL atoms are done in exactly the same way. You figure out how many electrons they have,
then keep going with the electron configuration 'addresses' until you have reached the right
number of electrons (and remember - the number of electrons is represented by the number
AFTER the letter; not before).
Try these: Do the electron configuration for helium and neon and chlorine using the chart on the
website. I'll give some space and do them at the bottom so that you can try them out.
He - 1s2
Ne - 1s2, 2s2, 2p6, 3s2, 3p6, 4s2
Cl - 1s2, 2s2, 2p6, 3s2, 3p5
Solution
Electrons have places around the atom that they are most likely to be. An electron configuration
is a way of describing these places, like an address for electrons. Each part of what you just
wrote out describes a place where electrons can be found in oxygen.
Let's take a look at just the first part: 1s2.
The '1' is the shell. The shell number is used to indicate how close to the nucleus the electrons
are. The first shell is the *closest* possible spot for the electrons - the higher this number
becomes, the farther away from the nucleus they go. The '1' shell MUST be get its electrons
before the '2' shell or '3' shell, and so on - it gets priority. With me so far? :)

3. The 's' is the subshell, which refers to the SHAPE of the area where the electron might be. 'S'
stands for 'spherical', like a beach ball. Imagine a sphere like that around the nucleus - electrons
in the 1s area can be anywhere on that shell.
Finally, we've got the '2' of 1s2. This indicates the number of electrons present. ALL 'S'
SHELLS CAN HOLD NO MORE THAN 2 ELECTRONS. EVER. So when you get to 2s? It
should have 2 electrons as well, when it's full. 3s? Should also have two electrons. ANYTHING
with an 's' should have up to two.
So, the fact that 1s comes before 2s comes before 2p? That must be memorized, unfortunately.
There is a handy chart to help you remember the correct order; you can find it here:
http://education.jlab.org/qa/electron_config.html.
Now we come onto how you do an electron configuration for a specific atom. Let's say your
teacher tells you to draw the electron configuration for oxygen. You look on the Periodic Table
(go ahead) and see that the number of electrons in an oxygen atom is eight. Now your job is to
use this code we've talked about to describe where each of those eight electrons is in an oxygen
atom.
You have to start putting electrons in the '1' shell because you always fill the 'lowest' (closest
to the nucleus) level first. So you have 1s2, two electrons in the first shell, darting around over a
sphere. That means you have two electrons so far. But oxygen has eight all together - the PT says
so. So we keep going. Again with the memorization, we know that 2s is next, and all 's'
subshells have up to two electrons. So we now have 1s2, 2s2. That's still only four electrons all
together. We have to keep going.
Next is 2p. 'p' subshells can hold up to six electrons. BUT, if we do six... 1s2, 2s2, 2p6...
adding up our electrons gives us 10. Oxygen only needs eight electrons! So we need: 1s2, 2s2,
2p4. Now we have 8 electrons all together.
ALL atoms are done in exactly the same way. You figure out how many electrons they have,
then keep going with the electron configuration 'addresses' until you have reached the right
number of electrons (and remember - the number of electrons is represented by the number
AFTER the letter; not before).
Try these: Do the electron configuration for helium and neon and chlorine using the chart on the

4. website. I'll give some space and do them at the bottom so that you can try them out.
He - 1s2
Ne - 1s2, 2s2, 2p6, 3s2, 3p6, 4s2
Cl - 1s2, 2s2, 2p6, 3s2, 3p5