Answers

2015-11-22T20:50:54+05:30

This Is a Certified Answer

×
Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
First of all, you need to understand what are ions.
Ions are simply atoms with a net electric charge on them.
Eg- H+,  Cl-

Polyatomic ions are a group of atoms containing a net electric charge.
Eg - NH+, OH-

Here, NH+ and OH- contain two atoms (or a group of atoms) each.

For formation of compounds with polyatomic ions, the ion is enclosed in a bracket to indicate the ratio.
Let me explain it with the help of an example.
Mg3(PO4)2 - Magnesium Phosphate
Here, a compound is made using Phosphate (PO4), which is polyatomic ion.

Since Mg has a valency 2 and PO4 has a valency 3, therefore we get the formula Mg3(PO4)2 by criss-cross method.
Phosphate here is a polyatomic ion and so we enclose it in a bracket to indicate its ratio, i.e, 2

0