6.
Explanation
Electron affinity is the energy change that occurs when an atom gains an electron to form a negative ion (anion). It is a measure of how much an atom or ion “likes” to accept an additional electron. A positive electron affinity indicates that energy is released when an electron is added, whereas a negative electron affinity indicates that energy is required to add an electron.
Noble gases, which include elements like helium (He), neon (Ne), argon (Ar), and others, have a zero or very close to zero electron affinity. This means that adding an electron to a noble gas atom neither releases energy nor requires energy—it is a nearly energy-neutral process. There are two primary
reasons for this:
1. Stable Electron Configuration: Noble gases already have full valence electron shells, which makes their electron configuration highly stable. For example, helium has two electrons in its outermost shell, which is the maximum for that shell. Gaining an additional electron would disrupt this
stable electron configuration.
2. High Ionization Energy: Noble gases have a high ionization energy, which means it takes a substantial amount of energy to remove an electron from a noble gas atom. Similarly, it also takes a substantial amount of energy to add an electron because the electron must be forced into an already tightly packed electron cloud.
Due to these factors, noble gases are typically unreactive and do not readily form chemical compounds through the addition or loss of electrons. Their stable, full electron shells make them chemically inert and less likely to participate in chemical reactions. This is why noble gases are often used in applications where chemical reactivity needs to be minimized, such as in lighting (neon signs) or as a non-reactive atmosphere in certain laboratory processes.