Answer
See the explanation
Work Step by Step
a. The sign of the energy change for each of the three processes is as follows:
(1) Removing an electron from the metal: This process requires energy, so the sign of the energy change is positive.
(2) Adding an electron to the nonmetal: This process releases energy, so the sign of the energy change is negative.
(3) Allowing the metal cation and nonmetal anion to come together: This process releases energy, so the sign of the energy change is negative.
b. In general, the sign of the sum of the first two processes is negative. This is because the energy released in the second process (adding an electron to the nonmetal) is greater than the energy required in the first process (removing an electron from the metal). This can be seen in the examples of NaCl and MgO, where the formation of the ionic compounds is exothermic (energy-releasing) overall.
c. The sign of the sum of the three processes must be negative. This is because the energy released in the second and third processes (adding an electron to the nonmetal and the formation of the ionic bond) is greater than the energy required in the first process (removing an electron from the metal).
d. Ionic bonds occur because the sum of the three processes is negative, meaning that the overall process is exothermic (energy-releasing). This makes the formation of the ionic compound favorable and stable.
e. NaCl is stable because the sum of the three processes is negative, resulting in an exothermic reaction and a stable ionic compound. However, $Na_{2}Cl$ and $NaCl_{2}$ are not stable because the sum of the three processes would be positive, making the formation of these compounds unfavorable.
In the case of MgO, the sum of the three processes is negative, resulting in a stable ionic compound. However, $MgO_{2}$ and $Mg_{2}O$ are not stable because the sum of the three processes would be positive, making the formation of these compounds unfavorable.
