1. Dichromate Ion (Cr₂O₇²⁻)
* Chromium (Cr): Chromium typically has a valency of +3 or +6. In the dichromate ion, it has a valency of +6.
* Oxygen (O): Oxygen always has a valency of -2.
* Finding the Valency of Dichromate:
* Let the valency of the dichromate ion be x.
* We have 2 Cr atoms (+6 each) and 7 O atoms (-2 each).
* The equation is: 2(+6) + 7(-2) = x
* Solving this gives us x = -2. Therefore, the valency of the dichromate ion is -2.
2. Ammonium Dichromate ((NH₄)₂Cr₂O₇)
* Ammonium Ion (NH₄⁺): Ammonium has a valency of +1.
* Dichromate Ion (Cr₂O₇²⁻): As we established earlier, this has a valency of -2.
* Finding the Valency of Ammonium Dichromate:
* The compound is neutral, meaning the sum of the valencies must be zero.
* There are two ammonium ions (+1 each) and one dichromate ion (-2).
* The equation is: 2(+1) + (-2) = 0
* This confirms the compound's neutrality.
Key Points:
* Valency is the combining power of an element or ion.
* In ionic compounds, the valencies of the ions must balance to create a neutral compound.
Let me know if you have any more questions about valency or other chemical concepts!
