Final answer:
The change in energy can be calculated using ionization energy and electron affinity by understanding that IE is always positive and corresponds to energy required to remove an electron, while EA can be negative, positive, or zero, reflecting energy changes when adding an electron. The overall energy change is found by subtracting IE from EA, with signs indicating the direction of energy flow.
Step-by-step explanation:
To calculate the change in energy using ionization energy (IE) and electron affinity (EA), you need to understand the conventions of each. The ionization energy is the energy required to remove an electron from a neutral atom to form a cation in the gaseous state. This process is always endothermic, meaning IE is always positive.
For the reaction A(g) → A+(g) + e¯, the energy required is the IE.
Conversely, electron affinity refers to the energy change when an electron is added to a neutral atom to form an anion, also in the gaseous state. The sign of the EA depends on the process: negative if energy is released (exothermic), positive if energy must be added (endothermic), or zero if neutral. Unlike IE, electron affinities can vary greatly among elements.
When an electron is added, as in A(g) + e¯ → A¯ (g), the energy change is equivalent to EA. A negative EA indicates that energy is released during the process.
Therefore, the overall energy change when removing an electron (ionization) and then adding an electron (electron affinity) can be calculated by taking the difference between EA and IE, ensuring signs are observed properly as they indicate the direction of energy flow.