# Can chloride donate an electron pair to silver(I)?

According to the Lewis dot structure of $$\ce{Cl-}$$, $$\ce{Cl-}$$ has octet fulfilled and should be able to donate a pair of electrons as it is a Lewis base. The Lewis dot structure of $$\ce{Ag+}$$ seems weird. As it is a Lewis acid, I should assume that it can accept a pair of electrons.

However, now the problem arises. If $$\ce{Cl-}$$ donates a pair of electrons to $$\ce{Ag+}$$, there should be a coordinate covalent bond between them. In reality, $$\ce{AgCl}$$ is an ionic compound, and there is no such coordinate covalent bond, so I'm a bit confused.

In simpler words, $$\ce{Ag+}$$ is a lewis acid.$$\ce{Cl-}$$ is a lewis base. Can $$\ce{Cl-}$$ donate an electron pair to $$\ce{Ag+}$$?

Could someone please point me in the right direction?

• Cl- ion is capable of donating electron pairs. See the question (...)
– user123510
Apr 24, 2022 at 11:22
• (...), and then see the answer.
– user123510
Apr 24, 2022 at 11:23

If $$\mathrm{Cl^-}$$ donates a pair of electrons to $$\mathrm{Ag^+}$$, there should be a coordinate covalent bond between them. In reality, $$\mathrm{AgCl}$$ is an ionic compound, and there is no such coordinate covalent bond, so I'm a bit confused.

Yes, there is no dative bond between them. $$\mathrm{AgCl}$$ is an ionic compound with partially covalent character. So, the bond between $$\mathrm{Ag^+}$$ and $$\mathrm{Cl^-}$$ will be a simple ionic bond.

In simpler words, $$\mathrm{Ag^+}$$ is a lewis acid. $$\mathrm{Cl^-}$$ is a lewis base. Can $$\mathrm{Cl^-}$$ donate an electron pair to $$\mathrm{Ag^+}$$ ?

Yes, $$\mathrm{Ag^+}$$ can act as Lewis acid and $$\mathrm{Cl^-}$$ can act as Lewis base. But actually $$\mathrm{Cl^-}$$ can't donate an electron pair to $$\mathrm{Ag^+}$$. This is because both are weak Lewis acids and bases.

If $$\mathrm{Ag^+}$$ can't accept an electron pair, how can it be a Lewis acid?

It may not accept an electron pair in this case. It doesn't mean that it isn't a Lewis acid. Lewis acid doens't mean that it can accept an electron pair from any type of ligands. For example, $$\mathrm{Na^+}$$ is also a Lewis acid. Eventhough it is a Lewis acid it frequently forms ionic compounds rather than forming covalent compounds.
I can give an example where $$\mathrm{Ag^+}$$ can act as a Lewis acid. $$\mathrm{AgCl}$$ is insoluble in water but it is soluble in ammonia. This is because $$\mathrm{AgCl}$$ forms complex with $$\mathrm{NH_3}$$ which accounts for its solubility. During formation of complex $$\mathrm{NH_3}$$ will donate an electron pair to $$\mathrm{Ag^+}$$. So here it acts as a Lewis acid. I can give its equation - $$\ce{ Ag+ + 2NH3 -> [Ag(NH3)2]+}$$

• According to the Wikipedia definition, a Lewis acid is one that can accept an electron pair. If Ag+ can't accept an electron pair, how can it be a Lewis acid?
– user123510
Apr 24, 2022 at 10:48
• Sorry, it is not actually a question posted here. It just for your clarification. Apr 24, 2022 at 10:52
• Okay I will include answers to this comments in my post. Apr 24, 2022 at 10:54
• @Infinite is it always true that weak lewis bases don't form dative bonds with lewis acids? Apr 24, 2022 at 13:18
• @Arpan no, it is not true. If cation has high charge density for example Cr(III) ion can act as LA in presence of Cl- ion. Apr 24, 2022 at 15:02

Chlorine $$\ce{(Cl)}$$ needs to gain one electron in order to complete its octet (forming the $$\ce{Cl-}$$ ion), while silver $$\ce{(Ag)}$$ needs to lose one electron (forming the $$\ce{Ag+}$$ ion). This is why it is an ionic reaction. Unlike in a covalent bond, the electrons aren't shared; they are donated, forming dissociated ions in solution:

$$\ce{Ag^+(aq) + Cl^-(aq) <=>> AgCl (v)}$$

Note that $$\ce{AgCl}$$ generally forms as a precipitate. The reaction is technically reversible, but only proceeds to a very limited extent in solution.

Indeed, as you noted, $$\ce{Ag+}$$ is a Lewis acid, and $$\ce{Cl-}$$ is a Lewis base. Therefore, a Lewis acid-base adduct can form between the two. In fact, this is precisely why $$\ce{AgCl}$$ precipitates in solution! The $$\ce{Ag+}$$ and $$\ce{Cl-}$$ ions hold tightly together, forming a bond that has an extremely high covalent character. The bond between them is very difficult to break apart, which is why $$\ce{AgCl}$$ forms as a precipitate rather than being solubilized in water.

• According to Wikipedia, "A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct." If Ag+ can't accept an electron pair, how is it a Lewis acid?
– user123510
Apr 24, 2022 at 9:22
• Thank you for responding, sir! However, I'm genuinely confused as to why Ag+ is a Lewis acid if it can't accept an electron pair.
– user123510
Apr 24, 2022 at 9:32