Question

How does the electron affinity vary in the first transition series?

Short answer

Question: Describe the electron affinity trend in the first transition series and explain the factors influencing this trend. Answer: In the first transition series, electron affinity generally increases as we move from Scandium to Chromium, due to the increase in effective nuclear charge as the 3d subshell is gradually filled. From Manganese to Zinc, the trend becomes irregular because of increased electron-electron repulsion within the partially filled 3d orbital, which reduces the overall attraction experienced by the incoming electron. The affinity for Zinc becomes 0 since the 3d subshell is fully filled.

Step-by-step solution

Define Electron Affinity

Electron affinity is the energy change when an electron is added to the outermost shell of an isolated gaseous atom to form a negative ion. It is usually expressed in units of electron volts (eV) or kilojoules per mole (kJ/mol). In general, electron affinity increases from left to right across a period in the periodic table and decreases down a group.

List the Elements in the First Transition Series

The first transition series consists of the following elements: 1. Scandium (Sc) 2. Titanium (Ti) 3. Vanadium (V) 4. Chromium (Cr) 5. Manganese (Mn) 6. Iron (Fe) 7. Cobalt (Co) 8. Nickel (Ni) 9. Copper (Cu) 10. Zinc (Zn)

Identify the Electron Affinity Trend

In the first transition series, the electron affinity generally increases as we move from Scandium to Chromium, then followed by a less regular trend from Manganese to Zinc. Let's look at the electron affinities of these elements: 1. Scandium (Sc): -18 kJ/mol 2. Titanium (Ti): -7.6 kJ/mol 3. Vanadium (V): -50.6 kJ/mol 4. Chromium (Cr): -65 kJ/mol 5. Manganese (Mn): -26 kJ/mol 6. Iron (Fe): -15 kJ/mol 7. Cobalt (Co): -64 kJ/mol 8. Nickel (Ni): -112 kJ/mol 9. Copper (Cu): -118.8 kJ/mol 10. Zinc (Zn): -0 kJ/mol

Explain the Electron Affinity Trend

The electron affinity trend in the first transition series can be explained by considering the atomic structure and electron configurations of these elements. From Scandium to Chromium, the electron affinity increases because the electrons are added to the same 3d subshell, which is gradually being filled. The increase in effective nuclear charge across the period causes the added electron to experience a stronger electrostatic attraction to the nucleus. For elements from Manganese to Zinc, the trend becomes irregular due to increased electron-electron repulsion within the partially filled 3d orbital. This repulsion reduces the overall attraction experienced by the incoming electron. Furthermore, the affinity for Zinc becomes 0 as the 3d subshell is fully filled, and it would require more energy to add an electron to the 4s orbital.

Key concepts

First Transition Series

When discussing the electron affinity trend, it's essential to start by understanding the first transition series, a critical segment in the periodic table. This series includes elements ranging from Scandium (Sc) to Zinc (Zn), occupying the 3d subshell in their atomic structures. These elements have unique properties, such as variable oxidation states and complex electron arrangements, which influence their chemical behaviors. As students, it's important to recognize that transition metals differ significantly from the main group elements due to these complex electron configurations.

Learning tip: Mentally visualize the position of these elements in the periodic table and their corresponding 3d subshell filling as you move from Scandium to Zinc. This imagery will help you remember the patterns in their properties, including electron affinities.

Periodic Table Electron Affinity

Electron affinity reflects the ability of an atom to accept an electron. Understanding this concept in the context of the periodic table is crucial for grasping chemical reactivity and trends among elements. Generally, electron affinity becomes more negative moving from left to right across a period. This occurs because added electrons are attracted by the increasing positive charge of the nucleus. However, this trend doesn't always hold true for transition metals, where factors such as subshell electron repulsion come into play.

When studying these trends, focus not just on the numbers but on the reasons why some elements deviate from the expected patterns. For instance, the irregularities observed from Manganese to Zinc in the first transition series are key topics to discuss when learning about electron affinity variations.

Atomic Structure and Electron Configurations

The atomic structure and electron configurations of elements significantly affect their electron affinities. For transition metals, the filling of the 3d subshell is a major factor impacting this property. In the initial part of the first transition series, the increase in electron affinity correlates with the filling of the 3d subshell and the simultaneous increase in nuclear charge, resulting in a stronger attraction for the incoming electron.

However, as the 3d subshell becomes more populated, electron-electron repulsion starts to play a more significant role. This results in the observed irregularities in the electron affinity values for elements in the latter part of the series. Remember to consider the interactions between electrons, the distribution within orbitals, and the overall energy of the system when studying electron affinities. These concepts link directly to properties such as magnetic behavior and catalytic activity, which are fundamental in many applications of transition metals.