Electron question

I’m confused again, is the outer level of an electron filled with 8? Also, how many electrons in Lithium?

If you look at the periodic table, you can get the number of protons in an element from the atomic number. For lithium, that would be 3. In order for an atom to be electrically neutral, it must have the same number of electrons as protons. So, a normal lithium atom has 3 electrons. But, a lithum ion could have more or less than 3.

As far as your first question, I think the answer is yes. But your wording makes me wonder if I’m reading it right. Do you mean are there 8 electrons in a complete electron shell? That’s true for most elements, at least.

You mean the outer level of an electron shell, I take it.

Except for hydrogen and helium, the outer electron shell of elements can indeed hold up to 8. Hydrogen and helium’s outer shell, 1s, can only hold 2.

CWB is correct. However, as a Chemistry grad, I feel compelled to relate that the Shell model of electrons is not widely used anymore, outside of HS chem classes. Similarly, we use Energy levels instead of the planetary model.

Physics grad checking in. Electrons occupy orbitals, really. Each “shell” has more and more available orbitals. Each higher orbital can hold more electrons. The orbitals are labeled s,p,d,f,g,h,… 2 electrons can occupy the s orbital, and each orbital can hold 4 more electrons than the previous one. (So p holds 6, d holds 10, f holds 14, etc.)

n=1: 1s (2 electrons)
n=2: 2s2p (8 electrons)
n=3: 3s3p3d (18 electrons)
n=4: 4s4p4d4f (32 electrons)

Most of the time, the electrons get filled in order, but there are exceptions. (i.e. 4s gets filled before 3d, 5s gets filled before both 4d and 4f, etc.)

So Lithium has two electrons in 1s, and one in 2s.
Li: 1s2s (only 1 in the 2s)
Potassium has 19 electrons. Two go in the first “shell”, eight go in the second, eight go in the 3s and 3p, and the last one goes in 4s instead of 3d (one of those weird exceptions). The full configuration is
K: 1s2s2p3s3p4s(only 1 in the 4s)

It’s almost simple.

That third paragraph should read “the orbitals get filled in this order”

Is the outer energy level of a noble gas full or half full?

Whoops, I think I found the answer, thanks to Encarta… sounds like a French dessert or something. Is the correct answer…FULL? I think it is. Let me know if I’m wrong:)

Yes, the outer shell of a noble gas atom is filled.

For a carbon atom, is the outer shell half full or half empty? Does the answer depend on whether you are an optimist or pessimist?

Why don’t y’all check out http://www.chemicalelements.com for all your elemetal conundrums?

I just love the way they used to teach us the Pauli Exclusion principle (that’s the one where electrons fill energy levels singly, before filling them in pairs)

Our textbook explained that it was like people getting on a bus - they filled the seats singly first and when all the empty seats were full, they would then start doubling up!

This analogy works in principle unless a good looking single female electron happens to be sitting on the bus.

So… ok.

It’s been said that each shell can hold more orbitals. But is each orbital limited to only 8 electrons? Excluding the first which is 2?

Their book, which is very dated, says that the first three energy levels contain 2,8,8 respectively.

They told me that their teacher explained how we now know there are 16e in the third, and 32e in the fourth.

Can someone explain in detail, what I should tell them.

So far I’ve heard “energy level”, “electron shell”, and “orbital”. Could someone clarify each of these for me. Are all the terms still used in modern science today?
Also, if someone could post that whole 1s2p… thing and show how many electrons each can hold, that would be wonderful. I had a chart like that in HS, but it is not in this book…

grr. they told me 18e in the third, not 16…

It appears Giraffe actually explained it very well. I guess I read it too fast the first time…

::sigh::

OK, here we go again. I get this up to a certain atomic number. But the elements with a lot of elevtrons is confusing me. Someone please explain:

What is the deal with these energy levels. Looking at a periodic table, it seems that the levels have
2
8
18
32
18
8
2

Then higher up it looks like
2
18
32
32
18
8
2

And then some of them are no filling up the previous level before filling the next, like

2
18
32
32
17
6
2
… or something like that.

What is the deal here. How exactly does one figure out how this should look. How can you find out the number of valence electrons just by knowing the total number of electrons? Why does it start getting smaller again if each orbital holds 4 more than the previous and each level holds more orbitals???
I tried to plug in the electrons into the 1s2s2p… and the last orbital I filled had like 5 or six in it, but the periodic table showed it had two valence electrons. The element I tried had atomic number 77.
How can one energy level, like the fourth, have 18 electrons in the lower elements but 32 in the higher ones? Is it because there are more electrons and the higher energy crams the electrons in there or something? How do you know when to start filling more than 18 in the fourth level?

I would really LOVE a detailed explaination of this. Maybe something I could print out, or a great link or something. It seems that no science teacher in this entire school knows the answer to this. All the gifted students are very curious and so is their teacher :rolleyes: . I told them I would be able to explain it all to them on Tuesday. (MLK Day on Monday.)

Ok people, no such thing as too much info here… any and all input is appreciated!

I believe you can find the total number of valence electrons by adding the total number of electrons in the outermost s and p orbitals. Since iridium, element 77, has two electrons in the 6s orbital, it has two valence electrons. To take the electron configuration, you would get 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d7 (or [Xe]6s2 4f14 5d7). Since 6 is the highest energy level, count the number of electrons in the s and p orbitals starting with the number 6 and you get the number of valence electrons in the element.

Now to energy levels. Energy levels are the quantitized energy states of the electrons. An electron orbiting an atom can be found in an energy level and nowhere else. It can’t be halfway between one energy level and another, for example. In those energy levels, there are sublevels which essentially show the places where the orbitals contained within can be found. The sublevels go by the wonderful names of s,p,d,f. So far, no element has been found that has more electrons than those that can be found in those sublevels. Each energy level adds one extra sublevel for each step up it takes. Level one has one sublevel s. Level two has sublevels s and p. Level three has sublevels s,p,d. And it goes on. Each sublevel has a number of orbitals that can be contained within the sublevel. Sublevel s has one orbital. Sublevel p has three orbitals. Sublevel d has five and sublevel f has seven. Each orbital can contain up to two electrons. To get the number of orbitals that can be contained in a given energy level, square the number of that level. The electrons fill these levels somewhat erratically. Level one fills up before level two does. Level two fills up before level three. However, the 4s orbital fills up before the 3d orbital does, with the 4p orbital following immediately after. 5s does the same thing to 4d, and 6s precedes 4f which precedes 5d which goes before 6p. 7s goes before 5f which goes before 6d which goes before 7p. No elements have been discovered which need more than that many electrons.
Level one has two electrons, level two has eight electrons, level three has 18 electrons, level 4 has 32 electrons. Square your level number and double it (two electrons per orbital) to get the total number of electrons in the level.

That probably doesn’t explain it too well, but I hope it helps a bit.

That explains it very well. But you stopped short. You stopped at:

Doesn’t this mean that level 5 should have 50 electrons, 6 should have 72, and 7 should have 98? Is this right?

Also, could someone give me the entire 1s2s2p… thing all the way through level 7 so I know what order to fill them in???

You guys rule.

Found this:

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6
BTW, I now understand everything. I have been practicing this stuff and I got them all right!! I am so freaking psyched right now!! I can’t wait to show everyone Tuesday. Can you believe that none of the teachers at the school knew this? I guess they are all used to the old models.
We touched on the spdf thing a little in high school, but that was my sophomore year. I dont think we got into it much at all in my one year of college chemistry.

Thanks again everyone. I am soooo happy!!!

Wraith pretty much said it all.

Yes, level n has 2n[sup]2[/sup] electrons. So, level 5 has 50, level 6 has 72, etc. Note that we’ve only discovered a finite number of elements, though, so you’ll never talk about an atom with a filled level 5.

You asked how higher levels can have fewer electrons with some elements than others. The answer is that the levels are made up of orbitals, which have different energies. The first few orbitals in a level (s,p) are much lower energy than the next few (d,f,g,etc.) At the higher levels, you’ll get overlap – the 4s orbital will be lower energy than the 3d orbital, for example.

As for the official electron filling order, it’s hard to illustrate here with just text. Go to this site. A lot of it is pretty high level, but if you go about half-way down, to the section titled “The Relative Energies of Atomic Orbitals”, there are two good figures showing how things get filled. A little farther down there is a table, showing the filling order of all the atoms.

Hopefully this answers your questions. If not, feel free to email me.