Forces acting among atoms - Structure of matter Flashcards
How can the dingin that a certain arrangement of electrons in the external shell yields higher stability be generalized?
The finding that a certain arrangement of electrons in the external shell yields a higher stability may be generalised by the following statement:
Chemical bonds among atoms is formed only in the case that such rearrangement of valance electrons of external shells occurs, which yields a higher stability.
Chemical bonds mostly do not cercern internal electrons.
How can the bonds among neutral atoms be explained?
The bonds among neutral atoms cannot be explained within the framework of classical physics.
The explanation was given by quantum mechanics and forces that create a covalent bond can be now quantitatively calculated.
Molecules are stable thanks to the fact that the energy of combined system of atoms is lower than that of the system of separated atoms.
Thus, if an interaction between atoms decreases their total energy then these atoms create a molecule.
If two atoms come near eachother, either covalet or ion bone can be formed, or no bond at all.
What are Born forces?
If electron shells overlap then they form one physical system and according to the Pauli principle, two electrons cannot exist in the same quantum state.
Thus, if some out of the interacting electrons are forced to occupy higher energy states as compared with those in separated atoms, the system would have higher energy and it would not be stable.
In such a case, the mutual approach of electrons results in appearance of repulsive Born forces.
These forces possess a very small range of action and drop with distance r proportionally to r-13.
