What Are Unpaired Electrons in Quantum Theory?

[404]

I'm doing the quantum theory in my class, and on the orbitals chapter... And a question in my book says "what are 'unpaired electrons'"? Do they mean what they are called? And even so, I don't know the answer

 

[Gokul43201]

Do you know about electronic confugurations and Hund's Rule ?

 

[ShawnD]

I'm doing the quantum theory in my class, and on the orbitals chapter... And a question in my book says "what are 'unpaired electrons'"? Do they mean what they are called? And even so, I don't know the answer

Unpaired electrons are the ones that can easily bond to things. Look at oxygen's valence. 6 electrons in 4 different orbitals. 2 of those orbitals are filled (2 each), and 2 orbitals have 1 electron each. Those electrons in their own orbitals are the unpaired electrons.

 

[selfAdjoint]

Every shell, whatever else it has, has the possibility of two electrons, one spin up on a given axis and the other spin down. Every electron possibility in the shell has this option, and if the two electrons are paired this way they are not easily available for bonding. But if a shell has an odd number of electrons, there is one that doesn't have a spin-opposite partner, and it is available for bonding.

 

[Pieter Kuiper]

Every shell, whatever else it has, has the possibility of two electrons, one spin up on a given axis and the other spin down. Every electron possibility in the shell has this option, and if the two electrons are paired this way they are not easily available for bonding. But if a shell has an odd number of electrons, there is one that doesn't have a spin-opposite partner, and it is available for bonding.

You are probably thinking of free radicals, but in the general case paired or unpaired electrons do not really have much to so with reactivity.

The two valence electrons of calcium are paired, but calcium is very reactive, as are the other alkaline Earth metals.

The unpaired electrons in the 4f shell of the rare Earth metals are not really involved in bonding at all.

 

[Dual Op Amp]

With the introduction of quantum physics, we learned that an electron orbits in place as well as orbitting around the nucleus. This causes an elevated energy level, dependent upon which way it is spinning. This energy level changes the quantum by 1/2 up or down, which is why two electrons can exist within the same sub-shell. This not only helps explain covelant bonding, but also explains magnetism. As the electron spins, it causes a magnetic field, this creates domains and then creates the magnet.

 

[Dual Op Amp]

Electrons are attracted to protons, but repell electrons. So, instead of all the electrons being bunched up right next to the nucleas, they orbit around the nucleas in shells. These shells can sometimes contain sub-shells. For example, the first shell contains only one sub-shell. As an electron gets further away from it's atom, it must have more "quantum energy." Electrons want to get as close to the nucleas as possible, but according to quantum physics, no to electrons can have the same "quantum energy." So, they orbit in shells. The electrons orbit in orbitals. The sub-shells have orbitals. For example, the 1 shell has an S orbital. Because it's an s orbital and it's the first shell it's labelled 1S. For 1-First shell-, S-S orbital. An S orbital has the shape of a sphere. An orbital wants to fill it's self. Alright, so why would the atom want to have 8 electrons in it's outer most shell, good question. The second shell has two sub-shells. One sub-shell has an S orbital, and the second has three P orbitals. The reason it has three is because they can arrange themselves according to X,Y,Z. Each orbital has only two electrons, because no two electrons can have the same "quantum energy." So, for the valence shell of an atom with two shells, one S orbital and three P orbitals. Two electrons an orbital adds to...8. Hydogen, on the other hand, only has one shell. So, to fill it's valence shell, it only needs two electrons. It already has one - Hydogen = one proton, one electron - so, it only needs to bond with one atom to fill itself. Carbon, on the other hand, has two shells, so it needs 8 to fill it's valence shell. So...

H
H C H Methane! CH4.
H

If you were to count it up everyone's filled. The carbon atom has 6 electrons. 2 in it's first shell, and 4 in it's valence shell. It needs 8 in it's valence shell. So, it shares one with hydrogen, and the hydrogen shares one of the carbons. This gives the carbon an extra electron, and the hydrogen it's desired two. The carbon, then, bonds with three more to add to 8.

HOH Water! H20. Oxygen has six valence electrons, meaning it needs 2 to gain, which it does with 2 hydrogen molecules.

O=O Oxygen! O2.

You're probably wondering, why is there an equals sign between the Oxygen molecules?
This indicated a double bond. Oxygen has six valence electrons, when it bonds with another oxygen, it gets 7. That's not the desired 8. So, it makes a double bond, and they share two electrons each. Which adds to 8.

O
O O Ozone! O3. Each one of these atoms share with each other, making 8.

That's covelant bonding!
This "quantum energy I told you about is somewhat true. What's really true is that there are four "quantum numbers" that cannot match.
The first is N.
N is the energy of an electron. For example, an electron in the first shell would have an N of 1. An electron in the second shell would have an N of 2. An electron in the third shell would have an N of 3.
N=1, means it's in the first shell.
The second is L. It's actually a greek cursive L kind of like this. l. Okay. This sign is the orbital. L = N - 1. That's the equation. So, if N = 1, then, L = 0. 0 is an S orbital.
If N = 2, L can equal either 0 or 1. If it is 1, that's a P orbital. If N = 3, then that can be either 0,1 or 2. An S,P or...a D orbital.
Now, the third quantum number is M. It is the orientation of the orbitals, you know XYZ.
M can equal anything between -L and +L. For example if L is 1, then M can equal -1,0,1.
This is 3 different ways of arranging the P orbital.
Now the final one is Ms. For Spin. The spin of the electron can equal - 1/2 or 1/2.

Okay, so let's look at the possible arrangements of some electrons.

N L M Ms
1 0 0 -1/2
1 0 0 1/2 First shell, only can have two electrons.

2 0 0 -1/2
2 0 0 1/2
2 1 -1 -1/2
2 1 -1 1/2
2 1 0 -1/2
2 1 0 1/2
2 1 1 -1/2
2 1 1 1/2 Second shell, eight electrons, but none of them, nor the one's in the first shell have the same 4 quantum numbers.

HOPE YOU UNDERSTAND. IT TOOK ME A WHILE TO WRITE, I'D HATE TO LOSE IT AT THE LAST MOMENT, LIKE THE POWER SHUT DOWN OR SOMETHING. IF YOU UNDERSTAND THIS, YOU WILL UNDERSTAND THE REST.
HERE'S SOME SITES.

http://chemed.chem.purdue.edu/gench...h6/quantum.html

http://lectureonline.cl.msu.edu/~mm...od/electron.htm