Which of the following is a Lewis acid ?

Options

A. `AlCl_(3)`
B. `MgCl_(2)`
C. `CaCl_(2)`
D. `BaCl_(2)`

Answer

A

Explanation

Alkaline earth metals form ionic chloride whereas aluminium chloride is covalent. Despite of sharing electrons with chlorine, the octet of aluminium is incomplete. To complete the octet, it needs electrons and thus, acts as a Lewis acid
`._(13)Al = 2,8,3 and ._(17)Cl = 2,8,7`
`{:(" "Cl),(" |"),(Cl-Al-Cl),(" "uarr),("Octet incomplete"):}`.