Which formula is an ionic compound?

An ionic compound is usually formed when both positive ions called a cation and a negative ion called an anion share electrons to create a bond. Therefore, you derive the correct formula of an ionic compound by canceling out the positive and negative charges of the ions.  

Explanation:

The formula of an ionic compound is achieved by following the steps below.

Step one.

choose the cation or the ion with the positive charge. These are metals and are placed on the left side of the periodic table.

Step two.

Choose the anion or the ion with the negative charge. These are non-metals.

Step three.

Put down the ion with the positive charge followed by the ion with the negative charge.

Step four.

Lastly, adjust both subscripts of the ions such that their net charge is zero. Then put down the formula by having the small number ratio between the positively charged ion and negatively charged ion to balance the charge.Examples include: sodium chloride  NaCl

Particle exchange energy though elastic collision , hope this .