Covalent bonds - Structure of matter Flashcards
What is the exchange effect?
One or more pairs of electrons appertain simultaneously to both atoms bound.
This is a consequence of a quantum mechanical effect called the exchange effect.
Explain the importance of spin in covalent bonds.
A very important property of the covalent bond is its dependence on the spin of electron and this bond is very strong if the directions of spins are antiparallel.
What is the saturation effect?
An important property of covalent bonds is the saturation effect since it is realised only by a couple of electrons.
In the covalent bond, only electrons of external not completly occupied shells can participate.
The electric charge is not distributed symmetrically in the molecule formed and the resulting molecule possesses electrical properties of a dipole.
Explain the energy contained in a covalent bond with relation to the hydrogen atom.
The covalent bond is the strongest out of all the types of bonds.
E.g.
The energy of the bond between two atoms of hydrogen is 4.3 eV.
This means, that just the energy 4.3 eV is released during the formation of a hydrogen molecule.
The energy 417kJ is released when forming 1 mole of H2.
The atoms bound by this type of bond are near together;
E.g.
The distance of protons in a hydrogen molecule is of 0.074nm whereas the radius of the internal path of electron in a hydrogen atom (Bohr’s radius) is ~=0.054nm.
Explain the binding energy
There is a certain distance between the atoms that form a molecule, at which the repulsive and attractive forces are equilibrated and this distance corresponds to a minimum potential energy of the system.
It is impossible to remove the atoms to larger distances or to approach them without supply of external work for increasing the energy of the system.
of course, the binding energy equals the amount of the energy released during the formation of this molecule.
