The phosphonium ion, PH₄⁺ is formed by reaction of phosphine, PH₃, with an acid.
d. Explain why the ion has a +1 charge.

Verified step by step guidance

1. Start by identifying the reactants: phosphine (PH₃) and an acid. Phosphine is a neutral molecule, and acids typically donate protons (H⁺ ions) in chemical reactions.
2. Understand the process of proton donation: When the acid donates a proton (H⁺), it is accepted by the phosphine molecule. This results in the formation of the phosphonium ion (PH⁺₄).
3. Examine the electron count: Phosphine (PH₃) has a lone pair of electrons on the phosphorus atom. When it accepts the proton (H⁺), the lone pair is used to form a bond with the proton, creating PH⁺₄.
4. Analyze the charge distribution: The proton (H⁺) carries a positive charge. Since phosphine is neutral, the addition of a positively charged proton results in the overall charge of the phosphonium ion being +1.
5. Conclude the explanation: The +1 charge on the phosphonium ion arises because the neutral phosphine molecule gains a positively charged proton during the reaction, without losing any electrons to counterbalance the added positive charge.

Key Concepts

Phosphonium Ion

A phosphonium ion, such as PH⁺₄, is a positively charged species formed when phosphine (PH₃) reacts with a proton (H⁺). In this reaction, the phosphine molecule donates a lone pair of electrons to the proton, resulting in the formation of the ion. This process is similar to the formation of ammonium ions from ammonia.

Charge of Ions

The charge of an ion is determined by the difference between the number of protons and electrons. In the case of PH⁺₄, the ion has one more proton than the number of electrons, leading to a net positive charge of +1. This charge indicates that the ion is electron-deficient, which is a characteristic of cations.

Acid-Base Reaction

An acid-base reaction involves the transfer of protons (H⁺ ions) from an acid to a base. In this context, phosphine acts as a base that accepts a proton from an acid, resulting in the formation of the phosphonium ion. Understanding this reaction is crucial for grasping how the charge of the resulting ion is established.