Which has the more negative electron affinity, Na or Cl?

Verified step by step guidance

Step 1: Understand the concept of electron affinity. Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous state to form a negative ion. A more negative electron affinity indicates a greater tendency to gain an electron.

Step 2: Consider the position of Na (sodium) and Cl (chlorine) on the periodic table. Sodium is in Group 1 (alkali metals), while chlorine is in Group 17 (halogens).

Step 3: Recall that halogens, like chlorine, have high electron affinities because they are one electron short of a full valence shell, making them very eager to gain an electron.

Step 4: Compare the general trends in electron affinity across the periodic table. Electron affinity generally becomes more negative across a period from left to right and less negative down a group.

Step 5: Conclude that chlorine, being a halogen, has a more negative electron affinity than sodium, as it is more inclined to gain an electron to achieve a stable octet configuration.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electron Affinity

Electron affinity is the amount of energy released when an electron is added to a neutral atom in the gas phase. A more negative electron affinity indicates a greater tendency for an atom to gain an electron, which is crucial for understanding the reactivity of elements, particularly in forming anions.

Trends in the Periodic Table

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across or down the periodic table. For electron affinity, it generally increases (becomes more negative) from left to right across a period and decreases down a group, which helps in comparing elements like sodium (Na) and chlorine (Cl).

Comparison of Alkali Metals and Halogens

Alkali metals, such as sodium, have low electron affinities because they prefer to lose an electron to achieve a stable electron configuration. In contrast, halogens like chlorine have high electron affinities, as they are one electron short of a full outer shell and readily gain an electron, making their electron affinity more negative than that of alkali metals.