Question

Consider the following statement: “Because oxygen wants to have a negative-two charge, the second electron affinity is more negative than the first.” Indicate everything that is correct in this statement. Indicate everything that is incorrect. Correct the incorrect statements and explain.

Short answer

The correct part of the statement is that oxygen wants to have a negative-two charge, as it gains two electrons to achieve a stable, full outer electron shell. The incorrect part is that the second electron affinity is more negative than the first. The corrected statement should be: "Because oxygen wants to have a negative-two charge, the first electron affinity is more negative than the second." This is because, when adding a second electron, the negative charge of the first gained electron repels the incoming electron, making the second electron affinity less negative than the first.

Step-by-step solution

Identify the correct parts of the statement

The statement given is: “Because oxygen wants to have a negative-two charge, the second electron affinity is more negative than the first.” Let's break it down into its components. The first part of the statement to consider is the claim that "oxygen wants to have a negative-two charge." This is, in fact, correct. Oxygen, with its six valence electrons, would ideally gain two more electrons to achieve a stable, full outer electron shell (eight electrons in total). Gaining these two electrons would result in a negative-two charge.

Identify the incorrect parts of the statement

The second part of the statement to consider is the claim that "the second electron affinity is more negative than the first." This statement is incorrect. The first electron affinity of an atom is typically more negative than the second electron affinity.

Correct the incorrect statement and provide explanation

Now, let's correct the incorrect part of the statement and provide an explanation. The corrected statement should be: "Because oxygen wants to have a negative-two charge, the first electron affinity is more negative than the second." The reason behind this is that electron affinity is the energy change that occurs when an electron is added to a neutral atom to form a negative ion. When the first electron is added, the atom's stronger positive charge on the nucleus attracts the electron, releasing energy (negative electron affinity). When a second electron is being added, the negative charge of the first gained electron repels the second incoming electron. Therefore, energy must be input in order for the second electron to be added (positive electron affinity). As a result, the first electron affinity is more negative than the second electron affinity.

Key concepts

Negative Charge

Atoms strive to achieve a stable electron configuration, often trying to mimic the electron arrangement of the nearest noble gas. A negative charge on an atom indicates that it has gained extra electrons.
Oxygen naturally attains a negative-two charge because it needs two additional electrons to complete its valence shell, achieving a configuration similar to neon.

• Oxygen generally forms a positive negative charge of -2 when it gains two electrons.
• This gain of electrons to form ions is a fundamental behavior in chemistry, aiding in creating more stable compounds.

When discussing negative charge, it's crucial to understand that this depends heavily on the atom's need to achieve balance.
Each gained electron increases the overall negative charge, tending towards increased stability for elements like oxygen that seek full valence shells.

Valence Electrons

Valence electrons are the outermost electrons in an atom and play a crucial role in how elements react chemically. These electrons determine the chemical properties and reactivity of an element.

• Oxygen, for instance, has six valence electrons.
• To achieve a full octet, oxygen needs two more electrons, making it highly reactive in forming bonds.

Valence electrons are key in electron affinity, the measure of an atom’s tendency to accept electrons.
Elements with nearly complete outer electron shells are often more eager to gain electrons, as is the case with oxygen.
Understanding valence electrons helps explain why certain reactions occur and why some elements form specific ion charges.

Energy Change

Energy change in electron affinity describes the energy released or absorbed when an atom gains an electron.
The process involves the atom's nucleus attracting the electron, and this attraction releases energy when the electron affinity is negative.

• The first electron affinity usually involves a release of energy, as the nucleus strongly attracts the first additional electron.
• For the second electron, the process might require energy input due to increased electron repulsion from the existing negative charge.

When oxygen gains its first electron, the energy change is quite negative, meaning energy is released.
However, adding the second electron requires overcoming the repulsion between like charges, thus requiring energy, resulting in a less negative or even positive electron affinity.