Why don't electrons fill the lowest energy orbitals first?

[Antymattar]

Hello. I recently read Theodore Gray`s book "The Elements" and was extremely fascinated by the small world of atoms. I was fascinated about the structure of atoms and wanted to know more about why and how they are composed.

After studying a bit I hit a bit of a curiosity. Why don some elements atoms don`t pack their electrons in a way so that they are not always as close to the core as possible? Is there an explanation to this? I was also very interested ion the lanthanide section of the periodic table. I heard that an element is defined by their outer ring of electrons, thought, that can clearely not be the case considering that the lanthanides have the same amount of electrons on the outer ring. So one must conclude that the inner electrons also define the element in some way.

Now what does this have to do with the title? I was wondering, would it be possible to assemble atoms in a way that you can define in what ring the electrons are located. Would it be possible to make a hydrogen atom but have it`s electron be somwhere in the 7p orbit?

If so then I soppose that that would create a completely new element with new properties.

I appologise for any bad grammar you may come across(I`m Latvian)

 

[DanP]

http://ocw.mit.edu/courses/chemistry/5-112-principles-of-chemical-science-fall-2005/video-lectures/

 

[Antymattar]

Wow! that's some good stuff there.

 

[Mapes]

Would it be possible to make a hydrogen atom but have it`s electron be somwhere in the 7p orbit?

If so then I soppose that that would create a completely new element with new properties.

Elements are determined by the number of protons (the atomic number). An atom with an electron in a higher-energy state is called an excited atom. (If the number of electrons doesn't match the number of protons, it's called an ion; if you adjust the number of neutrons, you create different isotopes.)

 

[Ygggdrasil]

After studying a bit I hit a bit of a curiosity. Why don some elements atoms don`t pack their electrons in a way so that they are not always as close to the core as possible? Is there an explanation to this? I was also very interested ion the lanthanide section of the periodic table. I heard that an element is defined by their outer ring of electrons, thought, that can clearely not be the case considering that the lanthanides have the same amount of electrons on the outer ring. So one must conclude that the inner electrons also define the element in some way.

Electrons pack in such a way as to minimize their energy. While distance from the nucleus is one important factor determining the energies of the orbitals, it is not the only factor. In atoms containing more than one electron, electron-electron repulsion also plays a role in determining the energies of the orbitals. These interactions are responsible for the fact that, say the 4s orbital has a lower energy than the 3d orbital even though the electrons in the 3d orbital are, on average, closer to the nucleus than electrons in the 4s orbital.

As Mapes mentioned, the identity of an element is by definition defined by the number of protons in its nucleus. However, the chemical properties of an atom are defined by the electronic structure of the outer shell of electrons. Therefore, atoms with similar outer electron configurations, such as the lanthanides, will have very similar chemical properties. In fact, the chemistries of the lanthanides are so similar that it is notoriously difficult to separate them from one another. In most cases, we cannot separate them based on chemical properties; rather, our separation methods must be based on their physical properties like the sizes of the atoms (and their ions).

 

[Nemus]

There are actually atoms like you describe. We call them excited states. When an atom abosrbs a photon it electrons arranges in a higher energy configuration. They are usually very shortlived and a photon is given off again. However, there are exceptions. Helium can be excited to a state with the electon spins parallell which can be kept for long periods, minutes if I remember correctly. It is called metastable helium. Google it, I am sure you'll find it interesting.