What is used to determine the number of each atom in an ionic formula

The charge carried by each ion (oxidation state of each atom)

Explanation:

If we have an ionic compound and we want to write its formula, we must first know the magnitude of charge on each ion (shown as oxidation state of the atoms involved) because the magnitude of charge on each ion is eventually crisscrossed and gives the subscript (number of atoms) for each atom in the formula.

For instance, let us write the formula of calcium bromide. Ca has a charge of +2 while Br has a charge of -1. If we exchange the charges and ignore the signs such that the crisscrossed charges form subscripts we can now write; .

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.