Question

an ionic compound is named ammonium phosphide. complete the table to determine the number of ions of each type in one formula unit of the compound. enter a negative sign before negative numbers. positive numbers do not need a positive sign.
ion \tcharge of one ion \ttotal charge of ion(s) in compound \tnumber of ion(s) in compound
ammonium \tyellow box \tyellow box \tyellow box
phosphorus \tyellow box \tyellow box \tyellow box
*in one formula unit
what is the formula for the ionic compound?
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Explanation:

Step1: Determine ammonium ion charge

Ammonium ion is $\ce{NH4^+}$, so charge of one ammonium ion is $+1$.

Step2: Determine phosphide ion charge

Phosphide ion is $\ce{P^{3-}}$, so charge of one phosphide ion is $-3$.

Step3: Balance charges for compound

Let number of $\ce{NH4^+}$ be $x$ and $\ce{P^{3-}}$ be $y$. Total positive charge: $x(+1)$, total negative charge: $y(-3)$. For neutral compound, $x(+1) + y(-3) = 0 \implies x = 3y$. The simplest ratio is $x = 3$, $y = 1$.

Step4: Fill table for ammonium

Charge of one ion: $+1$. Total charge (3 ions): $3\times(+1) = +3$. Number of ions: $3$.

Step5: Fill table for phosphide

Charge of one ion: $-3$. Total charge (1 ion): $1\times(-3) = -3$. Number of ions: $1$.

Step6: Determine formula

Formula is $\ce{(NH4)3P}$ (since 3 $\ce{NH4^+}$ and 1 $\ce{P^{3-}}$).

Table Completion:

Ion	Charge of One Ion	Total Charge of Ion(s) in Compound	Number of Ion(s) in Compound
Phosphide	$-3$	$-3$	$1$

Formula for Ionic Compound:

$\boldsymbol{\ce{(NH4)3P}}$

Answer:

(Table Values and Formula):

• Ammonium: Charge = $+1$, Total Charge = $+3$, Number = $3$
• Phosphide: Charge = $-3$, Total Charge = $-3$, Number = $1$
• Formula: $\ce{(NH4)3P}$