Draw the structures of `BCl_(3).NH_(3) and AlCl_(3)` (dimer).

Answer

In `BCl_(3)`, the central `B` atom has six electrons in the valence shell.It is therefore, an electron deficient molecule and needs two more electrons to complete its octet.It other words, `BCl_(3)` acts as a Lewis acid `NH_(3)`, on the other hand, has a lone pair of electrons which it can donate easily.Therefore, `NH_(3)` acts as a Lewis base.The Lewis acid `(BCl_(3))` and the Lewis base `(NH_(3))` combine together to form an adduct as shown below:
`(##RES_INO_CHM_XI_C06_E01_011_A01##)`
In `AlCl_(3),Al` has six electrons in the valence shell.Therefore, it is an electron deficient molecule and needs two more electrons to complete its octet.
`(##RES_INO_CHM_XI_C06_E01_011_A02##)`
Chlorine, on other hand, has three lone pair of electrones.Therefore to complete its octet, the central `Al` atom of one molecule accepts a lone pair of electrons from `Cl` atom of the other molecule forming a dimeric structure as shown above.