A non-metallic element of group 13, used in making bullet proof vests is extremely hard solid of black colour. It can exist in many allotropic forms and has unusually high melting point. Its trifluoride acts as Lewis acid towards ammonia. The element exhibits maximum covalency of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why does the trifluoride act as a Lewis acid.
The element being discussed is Boron. It has an extremely high melting point and is black in colour along with being extremely hard.
Reaction of Boron Trifluoride with ammonia: -
Monomeric trihalides are deficient in the electrons, thus they act as strong Lewis acid. In order to complete the octet of boron, trifluoride of boron reacts conveniently with Lewis bases like . Due to the absence of d electrons in boron, it is not able to exceed the above mentioned covalence.