((|Vtrue-Vobserved|) / (Vtrue)) x 100
1.77777%error
Answer:

Explanation:
In this question, we wish to find the missing nuclei for the equation:

In order to find the missing species, we need to use the charge and mass balance law. That is, the mass should be conserved: the total mass on the left-hand side with respect to the arrow should be equal to the total mass on the right-hand side with respect to the arrow:

Notice from here that:

So far we know that the mass of X is 4. Similarly, we apply the law of charge conservation. The total charge should be conserved:

From here:

We have a particle:

Looking at the periodic table, an atom with Z = 2 corresponds to helium. This can also be written as an alpha particle:

The reactions based on the absorption and release of the energy are called endothermic and exothermic reactions. The reaction is exothermic.
<h3>What is an exothermic reaction?</h3>
Exothermic reactions are the reaction in which the reactant produces products that release energy from the system to the surroundings. In the reaction bond energy of the reactant is less than the product.
Energy from the system is released in the form of heat, sound, light and electricity. The weak bonds of the compounds are replaced with stronger ones and the standard enthalpy of the reaction is negative.
Therefore, option c. reaction is exothermic is correct.
Learn more about the exothermic reactions here:
brainly.com/question/26616927
the answer is 5.6 because you have to move the decimal to the left three times