Phosphorus(V) chloride, PCl5
In the case of phosphorus, 5 covalent bonds are possible - as in PCl5.
Phosphorus forms two chlorides - PCl3 and PCl5. When phosphorus burns in chlorine both are formed - the majority product depending on how much chlorine is available. We've already looked at the structure of PCl3.
The diagram of PCl5 (like the previous diagram of PCl3) shows only the outer electrons.
Notice that the phosphorus now has 5 pairs of electrons in the outer level - certainly not a noble gas structure. You would have been content to draw PCl3 at GCSE, but PCl5 would have looked very worrying.
Why does phosphorus sometimes break away from a noble gas structure and form five bonds? In order to answer that question, we need to explore territory beyond the limits of most current A'level syllabuses. Don't be put off by this! It isn't particularly difficult, and is extremely useful if you are going to understand the bonding in some important organic compounds.
 


































Comments











Post a Comment



















Popular posts from this blog




























 A chemical bond  is an attraction between atoms  that allows the formation of chemical substances  that contain two or more atoms. The bond is caused by the electrostatic force  of attraction between opposite charges, either between electrons  and nuclei , or as the result of a dipole  attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent  or ionic bonds  and "weak bonds" such as dipole–dipole interactions , the London dispersion force  and hydrogen bonding .  








Read more




























Image







  Boron trifluoride, BF 3      A boron atom only has 3 electrons in its outer level, and there is no  possibility of it reaching a noble gas structure by simple sharing of  electrons.  Is this a problem?  No.  The boron has formed  the maximum number of bonds that it can in the circumstances, and this is a perfectly valid structure.    Energy  is released  whenever a covalent bond is formed.  Because energy is being lost from  the system, it becomes more stable after every covalent bond is made.   It follows, therefore, that an atom will tend to make as many covalent  bonds as possible.  In the case of boron in BF 3 , three bonds is the maximum possible because boron only has 3 electrons to share  








Read more





























 Metallic bonding  constitutes the electrostatic attractive forces between the delocalized electrons , called conduction electrons , gathered in an electron cloud and the positively charged metal ions. Understood as the sharing of "free" electrons among a lattice  of positively charged ions ( cations ), metallic bonding is sometimes compared with that of molten salts ; however, this simplistic view [ which? ]  holds true for very few [ which? ]  metals . In a more quantum-mechanical  view, the conduction electrons divide their density equally over all atoms that function as neutral (non-charged) entities. [ citation needed ]  Metallic bonding accounts for many physical properties  of metals, such as strength , ductility , thermal  and electrical conductivity , opacity , and luster . [ 1 ] [ 2 ] [ 3 ] [ 4 ]   Although the term "metallic bond" is often used in contrast to the term " covalent bond ", it is preferable [ by whom? ]  to use the term metallic bon...








Read more