How does Phosphorus Pentachloride bond?

The thing I am having trouble with: why does $\small\ce{PCl4}$ form a +1 ion and $\small\ce{Cl}$ a -1 ion?




There is no ionic bonding that occurs, the phosphorus is able to make a hybrid orbital out of its $\small3s$ and $\small3p$ electrons, along with an empty $\small d$ orbital to form 5 $sp^3d$ molecular orbitals, of equal energy, which yields 5 spots for bonding electrons.


This is a known exception to the octet rule. 


![enter image description here](https://i.stack.imgur.com/dboy4.png) 


(graciously borrowed from [here](http://www.chemguide.co.uk/atoms/bonding/covalent.html))


 3

phosphorus has 5 valence electrons.each chlorine has 7 valence electrons.phosphorus give 1 electron to each chlorine and hence all the 6 attain 8 electrons in the outer shell thus forming an ionic bond. 


 -1