Covalent bonds show ionic properties

Ionic bond, covalent bond and metal bond in the type discussed are idealizations, extreme forms of. There are many molecules and solids in which these bonds are largely in pure culture, but in the general case there are bonds. Examples of this:Mix of.In the case of metals, a covalent component can still be present in spite of the metal bond, so that directed forces come into play when the atoms are arranged to form a solid - e.g. in iron (Fe); this has consequences for the resulting crystal structure.Mix of.For metals that consist of two types of atoms (this is called Alloys or intermetallic compounds) bond components usually occur, especially if the metals differ greatly in their electronegativity. Because then there will be a certain electron transfer to the more electronegative element; the atoms then differ in their charge state.So have for example Al - Li Alloys have a strong ionic component (electronegativityAl or Li= 1,5 or. = 1,0; while Al - V Alloys only have metallic bonds (electronegativity of V = 1.5 how Al)Mixture of Bond.Non-metals, e.g. oxides such as SiO2, or semiconductors and semi-metals like GaAs or SnO2, have covalent and ionic components. Again, the ionic component increases with the difference in the electronegativity values.The covalent part Ko can be estimated using the following rule of thumb
Ko  =   exp - 0.25 (X)2
It is X the difference in electronegativity values.As an example, we determine the proportion of covalent bonding in quartz (SiO2). The electronegativity values ​​of Si and O are approx. 1.8 and 3.5, respectively. This results from the above equation
Ko  =   exp - 0.25 (3.5 - 1.8)2  =  0,486
This means that about "half" of the bond has a covalent character. The consequence is that the directional dependence of the covalent bond in the SiO2 determines the crystal structure.

© H. Föll (MaWi 1 script)