# Electron Configuration of Filled Valence Electron Orbitals

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1. Jun 29, 2015

### Dong Aleta

Hi!

I have understood how elements such as Be and Ca, with fully filled 2s orbitals, are not to be considered "noble" because they still have unfilled p orbitals. But I'm having trouble understanding how these elements participate in chemical reactions without having any unpaired electrons.

My understanding is that for an atom to bond (ionically or covalently) it has to have an unpaired electron. Is that incorrect? If yes, can you please explain how? Thanks so much!

2. Jun 30, 2015

### DrDu

The energetic difference between s and p orbitals is quite low in these elements so that the energy required to promote an s electron to a p orbital before bonding is made up by the energy gained in bonding.

3. Jun 30, 2015

### Dong Aleta

Does that mean that elements such as Be and Ca have a different mechanism for forming bonds, different than those of, say Na with an unpaired 3s1 electron and Cl with another unpaired 3p5 electron?

4. Jun 30, 2015

### DrDu

Not really. But in Be or Ca, you have to start (at least conceptually) from an excited state of the atom, i.e. Be 2s$^2$ -> Be 2s$^1$2p$^1$.

5. Jun 30, 2015

### Dong Aleta

Oh I see! I get it now. Thank you so much! I really appreciate the assistance. :D