Problem 51 - Chemistry Central Science

Question

The first ionization energy of Ar and the electron affinity of \(\mathrm{Ar}\) are both positive values. What is the significance of the positive value in each case?

Step-by-Step Solution

Answer

The positive values of the first ionization energy and electron affinity of Argon (Ar) signify its stable nature and reluctance to participate in chemical reactions by gaining or losing electrons. This is a characteristic of noble gases, as they have entirely filled valence electron shells, making them chemically inert and not likely to form bonds with other atoms.

Step 1: Understanding Ionization Energy

Ionization energy is the energy needed to remove an electron from an isolated gaseous atom or ion. A positive ionization energy value means energy must be supplied to the system to remove an electron from the atom. In the case of Argon (Ar), which is a noble gas with a full configuration of \(3s^2~3p^6\), it is already stable and does not want to lose any electron. Therefore, the first ionization energy of Ar being positive signifies that it's resistant to losing an electron.

Step 2: Understanding Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to an isolated gaseous atom or ion. It represents the measure of the attraction between the incoming electron and the nucleus. A positive electron affinity value indicates that energy is released when an electron is added to the atom. In the case of Argon (Ar), a positive electron affinity means that it is energetically unfavorable for Ar to gain an electron.

Step 3: Significance of Positive Values

The significance of the positive value of both the first ionization energy and electron affinity for Ar is that Argon is a highly stable atom in the periodic table. It is reluctant to either gain or lose an electron, which is a characteristic of noble gases. This stability is due to the fact that its valence electron shell is entirely filled, making it chemically inert and not likely to form bonds with other atoms. In summary, the positive values of the first ionization energy and electron affinity of Argon indicate its stable nature and reluctance to participate in chemical reactions by gaining or losing electrons.