Question

Order the atoms in each of the following sets from the least exothermic electron affinity to the most. a. S, Se b. F, Cl, Br, I

Short answer

a. The order of least exothermic electron affinity to most for S and Se is: Se < S. b. The order for F, Cl, Br, and I is: I < Br < Cl < F.

Step-by-step solution

Identify the position of S and Se in the periodic table

S (Sulfur) and Se (Selenium) are located in Group 16 of the periodic table. Sulfur is in the 3rd period while Selenium is in the 4th period.

Determine the trend in electron affinity for S and Se

Since Sulfur and Selenium are in the same group (Group 16), we use the trend that electron affinity decreases as we move down a group. Therefore, Sulfur should have a higher electron affinity than Selenium.

Order the atoms from least to most exothermic electron affinity

Based on the trend, the order from least exothermic electron affinity to most exothermic electron affinity should be Se < S. b. Ordering F, Cl, Br, and I based on their electron affinity

Identify the position of F, Cl, Br, and I in the periodic table

F (Fluorine), Cl (Chlorine), Br (Bromine), and I (Iodine) are located in Group 17 of the periodic table. They are in the 2nd, 3rd, 4th, and 5th periods, respectively.

Determine the trend in electron affinity for F, Cl, Br, and I

Since these atoms are in the same group (Group 17), we can use the trend that electron affinity decreases as we move down a group. As we move down from Fluorine (F) to Iodine (I), the electron affinity should decrease.

Order the atoms from least to most exothermic electron affinities

Based on the trend, the order from least exothermic electron affinity to most exothermic electron affinity should be I < Br < Cl < F.

Key concepts

Periodic Table

The periodic table is a fascinating tool that organizes all known chemical elements based on their atomic number, electron configurations, and recurring chemical properties. In this organized chart, elements are arranged in rows called periods and columns known as groups or families. Each element in a period has the same number of atomic orbitals, while elements in a group share similar valence electron configurations.

When studying the periodic table in relation to electron affinity, it’s important to understand position. For instance, in the case of Sulfur (S) and Selenium (Se), both located in Group 16, we see that Sulfur is in the 3rd period and Selenium in the 4th period. Similarly, elements such as Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I) are part of Group 17 and occupy successive periods starting from the 2nd up to the 5th period.

This layout helps predict how elements might behave in chemical reactions, including their tendencies in electron affinity, by observing trends observed down groups or across periods.

Group Trends

Group trends refer to the predictable patterns that occur down a column (or group) of the periodic table. These trends are related to properties such as atomic size, ionization energy, and importantly for our discussion, electron affinity.

Electron affinity is the energy change that occurs when an electron is added to a neutral atom. As one moves down a group, electron affinity generally decreases. This is because the added electron is farther from the nucleus and thus experiences less attraction due to increased atomic size and electron shielding.

Taking Group 16 with Sulfur and Selenium as an example, Sulfur has a more exothermic electron affinity compared to Selenium. This means that Sulfur releases more energy when it gains an electron. This same trend is observed in Group 17 elements like Fluorine, Chlorine, and Iodine. Fluorine, being at the top of its group, has the most exothermic electron affinity, while Iodine at the bottom has the least.

Exothermic Reactions

Exothermic reactions are processes that release energy, typically in the form of heat. In the context of electron affinity, when an atom accepts an electron and releases energy, this process is exothermic.

The more exothermic the reaction, the more energy is released. Thus, an element with higher electron affinity indicates a more exothermic reaction as the atom attracts additional electrons more strongly. For instance, Fluorine in Group 17 possesses a highly exothermic electron affinity. When Fluorine gains an electron, it releases more energy compared to its group neighbors like Chlorine or Bromine.

This release of energy is crucial in chemical processes as it usually indicates a favorable and spontaneous reaction under certain conditions. Understanding which elements have higher or more exothermic electron affinities can help predict their chemical behavior and reactivity in various contexts.