Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: aniond on February 08, 2014, 08:49:12 PM
-
I thought I understood bonding and lone pairs, now however I'm puzzled about a few things.
Let's take an oxygen atom for example. These are my assumptions, please tell me where I'm going wrong.
1) It has 6 valence electrons, or 3 lone pairs, by itself.
2) If it encounters two hydrogen atoms, it will form a full shell with 8 valence electrons, and become stable. Eg: H-O-H
3) The reason for this is because each hydrogen atom is donating an electron to fill its shell to a stable state.
Now my question is, what would happen hypothetically if 6 protons interacted with the oxygen atom. Since it has 6 valence electrons, why could these valence electrons not bond with 6 different protons (6H+) to form H6O? Since the protons would not be donating any electrons, the oxygen atom would remain at 6 valence electrons no? And this being unstable, two neutral hydrogen atoms could then bond to share their electrons to create a full valence shell to make H8O?
I realize this isn't possible, but why is it that an atom is limited to 4 bonds or less, if for example it interacts with a cation that isn't donating any electrons to give it a full shell?
-
1) It has 6 valence electrons, or 3 lone pairs, by itself.
Not really. In the lone atom, there are six valence electrons. Two would go into filling the 2s orbital, and the other 4 would be distributed among the four 2p orbitals. Because of Pauli Exclusion Principle, two of these remain unpaired. (E.g., one filled 2p orbital and two half-filled 2 orbitals.)
2) If it encounters two hydrogen atoms, it will form a full shell with 8 valence electrons, and become stable. Eg: H-O-H
OK, although at this point (see #3), atomic valence doesn't really have a well-defined meaning.
3) The reason for this is because each hydrogen atom is donating an electron to fill its shell to a stable state.
You just have to be careful with your language. Hydrogen's valence electron is not donated to oxygen. It remains shared between oxygen and hydrogen.
Now my question is, what would happen hypothetically if 6 protons interacted with the oxygen atom. Since it has 6 valence electrons, why could these valence electrons not bond with 6 different protons (6H+) to form H6O? Since the protons would not be donating any electrons, the oxygen atom would remain at 6 valence electrons no? And this being unstable, two neutral hydrogen atoms could then bond to share their electrons to create a full valence shell to make H8O?
Because to do this you'd have to promote some of oxygen's valence electrons up into higher atomic orbitals, which would take a fair bit of energy. Thermodynamics wins the day.
I realize this isn't possible, but why is it that an atom is limited to 4 bonds or less, if for example it interacts with a cation that isn't donating any electrons to give it a full shell?
It's not - plenty of atoms have valencies higher than four. Sulfur hexafluoride, for example, has a sulfur atom with six bonds.
-
Thanks for explaining that Corribus. I feel like I need to study a bit more about the orbitals to get a more intuitive understanding.
-
the geometrical structure of orbitals doesn,t support those many bondings