Which of the following pairs of chemical species consists entirely of Lewis acids?

Step-by-step solution

Lewis acids are chemical species that can accept an electron pair. SiF₄ has empty d-orbitals in the valence shell of the central silicon atom, allowing it to accept electron pairs and expand its octet (for example, forming [SiF₆]²⁻ ). Thus, it acts as a Lewis acid. BF₃ is an electron-deficient molecule with an incomplete octet on the central boron atom, making it a strong electron pair acceptor. Thus, it also acts as a Lewis acid. In the other options: H₂O is a Lewis base due to the lone pairs on the oxygen atom. N