Re: electron Configurations!?!

Cafegurl · Posted: Thu Mar 31, 2005 3:10 am Post subject: Re: electron Configurations!?!

[b]How Do i create electron configurations from the table of elements the long and short way?

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Mitch · Regular Joined: 25 Mar 2005 Posts: 29 Location: Berkeley

In the suggestion forum you should tell them to add electron configurations to their periodic table. Most periodic tables on the net should have them.

bluey_3 · Member Joined: 22 Aug 2005 Posts: 14

long way? no idea.
short way. maybe this:

from the periodic table, you get to know the number of protons = number of electrons.
e.g Na has 11 protons = 11 electrons
so the configuration is 2.8.1

or you can just see it from the table.
e.g Na is in group 1 and period 3. and so the configuration is 2.8.1

and from that configuration, we know its electron configuration is
1s2 2s2 2p6 3s1.

RobJim · Posted: Thu Aug 25, 2005 12:01 am Post subject:

I think "the short way" for sodium for example is this:

[Ne]3s1

Cafegurl, open up the periodic table from this website in a different window. Now, imagine He was placed in group II next to H and above Be. It sort of belongs there as well as where it is. It's kind of complicated why, but for this purpose, put it right above Be.

Now, find the element you want to figure out the electron configuration for. For example, Cl. Groups I and II make up the "s-block" which means their outermost electrons are in an S orbital. Groups III-VIII are the p-block, and the purple ones are the d-block. The orange ones are the f-block.

Start at H and count to the right. You'll go through two elements in the s-block in the first period, so you write 1s2. The 1 is for the first period, the s is for s-block, the 2 is for 2 electrons. Once you've done this, you have finished the first period, so go to the next. Now you count 2 more in the s-block, so write 1s2 2s2. Then, counting across, you get 6 p electrons in the second period, so you write 1s2 2s2 2p6. Then, the third period; 1s2 2s2 2p6 3s2 3p5. That is "the long way" of writing the electron configuration for Cl.

"The short way" would be to count back to the last noble gas (period VIII element) before your element and then summarize the electrons up to that element with [XX], in which XX is the symbol for the element. For Cl, the short way would be [Ne] 3s2 3p5. He counts as a Group VIII element for this purpose since it has a full valence shell.

The d- and f-blocks are slightly more complex, so make sure you can do the elements up to Ca well before you worry about the rest.