Write down the equation of the chemical reaction of combustion of a substance with serial number 15.

If we look at D.I. Mendeleev, then at number 15 we will see the substance phosphorus. Which has the chemical formula R. Combustion of phosphorus, like any substance, is, from a chemical point of view, the interaction of a substance with oxygen. The reaction of phosphorus combustion can be of two types. With an excess of oxygen and with a deficiency, two different substances are formed. Consider both reactions:

Combustion reaction with a lack of oxygen:
4 P + 3 O2 = 2 P2O3

When the reaction proceeds, trivalent phosphorus oxide is formed.
Combustion reaction with excess oxygen:
4 P + 5 O2 = 2 P2O5

When the reaction proceeds, pentavalent phosphorus oxide is formed.