Question

Arrange \(0, S\) and Se in the increasing order of their electron affinity. (1) \(\mathrm{Se}<\mathrm{S}<\mathrm{O}\) (2) \(\mathrm{O}<\mathrm{Se}<\mathrm{S}\) (3) \(\mathrm{S}<\mathrm{O}<\mathrm{Se}\) (4) \(\mathrm{S}<\mathrm{Se}<\mathrm{O}\)

Short answer

Option (1) \ \( \text{Se} < \text{S} < \text{O} \)

Step-by-step solution

Understand electron affinity

Electron affinity is the amount of energy released when an atom in the gaseous state accepts an electron to form an anion.

Identify periodic trends

Electron affinity generally increases across a period and decreases down a group in the periodic table.

Locate the elements in the periodic table

Oxygen (O), Sulfur (S), and Selenium (Se) are in Group 16, with Oxygen at the top, followed by Sulfur, and then Selenium.

Compare electron affinities

Oxygen has higher electron affinity than Sulfur, and Sulfur has higher electron affinity than Selenium. Thus, the order is \ \( \text{Se} < \text{S} < \text{O} \).

Verify with options

Option (1) \ \( \text{Se} < \text{S} < \text{O} \) matches the order derived from periodic trends.

Key concepts

periodic trends

Periodic trends refer to patterns in the properties of elements across different periods and groups in the periodic table. One important periodic trend is electron affinity, which typically increases across a period and decreases down a group. This occurs because atoms get smaller and nuclear charge increases as you move across a period, making it more energetically favorable to add an electron. Conversely, as you move down a group, atoms get larger and the added electron feels less attraction to the nucleus, resulting in lower electron affinity.

group 16 elements

Group 16 elements, also known as the chalcogens, include Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), and Polonium (Po). These elements share common properties due to their similar electron configurations.

• Oxygen is the most electronegative and has the highest electron affinity in the group.
• Moving down the group, the size of the atoms increases and electron affinity generally decreases.
• For the elements in question, Oxygen has the highest electron affinity, followed by Sulfur, and then Selenium.

This trend informs us about their reactivity and ability to form anions.

chemical periodicity

Chemical periodicity is the recurring pattern in the properties of elements revealed in the periodic table. It helps us predict how elements will behave based on their position in the table. Elements in the same group often exhibit similar chemical behaviors due to having the same number of valence electrons. For instance, in Group 16:

• All elements tend to form -2 anions.
• They show a decrease in electron affinity as you move down the group.
• Electron affinity is a key factor in determining how elements interact with others, affecting their chemical reactivity and the types of bonds they form.

Understanding these patterns allows us to predict properties and behaviors of elements not only in isolation but also in compound formation.