atoms form a molecule by using different types of communication.They differ in direction and energy, with which you can establish this relationship.

quantum-mechanical model of the covalent bond

covalent bond is formed by the valence electrons.When two atoms there is overlap of the electron clouds.The electrons of each atom begin to move in an area belonging to another atom.In the space around them, there is an excess negative potential which pulls positively charged nucleus.This is possible only under the condition that the total electron spins are antiparallel (pointing in different directions).

covalent bond is characterized by relatively high value of the binding energy per atom (about 5 eV).This means that it takes 10 eV to two atoms of the molecule, formed by covalent bond broke.Atoms can co
me closer to each other on a strictly defined state.With such a convergence is observed overlapping of electron clouds.The Pauli exclusion principle states that around the same atom can not rotate two electrons in the same state.The more there is overlap, the more the atoms repel each other.

hydrogen bond

This is a special case of a covalent bond.It consists of two hydrogen atoms.It is an example of this element in the twenties of the last century was shown the mechanism of formation of a covalent bond.The hydrogen atom is very simple in its structure, which allowed scientists to exactly solve the Schrodinger equation.

ionic bond

Crystal well-known salt formed by means of an ionic bond.It occurs when the atoms that make up molecules having a large difference in electronegativity.Less electronegative atom (in the case of the crystal salt is sodium) gives all its valence electrons of chlorine, becoming a positively charged ion.Chloro, in turn, becomes negatively charged ion.These ions are bound in the structure of an electrostatic interaction, which is characterized by a fairly large force.That is why the connection has the highest ionic strength (10 eV per atom, which is two times greater than the energy of a covalent bond).

in ionic crystals is very rarely observed defects of various kinds.Electrostatic interaction firmly holds the positive and negative ions in certain places, giving a vacancy, ofinterno- dal and other defects in the crystal lattice.