Electron Affinity (Ea)

• Electron Affinity is the energy change that occurs when an electron is added to a neutral gaseous atom to form a negatively charged ion.
• It is measured in kilojoules per mole (kJ/mol).
• A positive value of Ea indicates an energy release, while a negative value indicates energy absorption.

Trend in Electron Affinity for d-block Elements

• The Electron Affinity of d-block elements generally increases across a period.
• This is due to the increased effective nuclear charge, which attracts the added electron more strongly.
• However, there are exceptions and irregularities in this trend.

Explanation for Irregularities

1. Repulsion between electrons: When a new electron is added to a d-block element, it may experience repulsion from the already present electrons. This can lead to a decrease in Electron Affinity.

2. Subshell stability: The stability of half-filled and fully-filled subshells can also affect Electron Affinity. These configurations are more stable and therefore exhibit lower Electron Affinity.

Examples of Irregularities in Electron Affinity

1. Chromium (Cr): Cr has an Electron Affinity of -64 kJ/mol, which is lower than expected. This is due to the stability of a half-filled d subshell (4s^13d^5).

2. Copper (Cu): Cu has an Electron Affinity of -119 kJ/mol, which is significantly lower than expected. This is also due to the stability of a half-filled d subshell (4s^13d^10).

Representation of Electron Affinity Trends

• The Electron Affinity values can be plotted on a graph to observe the trend across a period or a group.
• The graph generally shows an increasing trend across a period, except for irregularities mentioned earlier.

Interpretation of the Electron Affinity Curve

• The curve of the Electron Affinity across the d-block elements indicates the variations in Electron Affinity as we go from left to right in a period.
• The irregularities in the curve can be explained by the factors discussed earlier.

Uses of Electron Affinity

• Understanding the Electron Affinity trends is important in predicting the chemical behavior and reactivity of d-block elements.
• It helps in explaining the formation of ionic compounds and the stability of different oxidation states.

Examples of Electron Affinity in Chemical Reactions

1. Formation of an oxide: The Electron Affinity of d-block elements can influence the formation of oxides, such as the reaction of Iron (Fe) with oxygen to form Fe2O3.

2. Formation of halides: The Electron Affinity also plays a role in the formation of halides, such as the reaction of Copper (Cu) with Chlorine (Cl) to form CuCl2.

Summary

• The Electron Affinity of d-block elements generally increases across a period.
• Irregularities in the curve are due to repulsion between electrons and subshell stability.
• Understanding Electron Affinity is important in predicting chemical behavior and reactivity.
• It plays a role in the formation of oxides and halides.

Slide 11

• The f-block elements are also known as inner transition metals.
• They are located at the bottom of the periodic table.
• The f-block elements have partially filled f orbitals in their valence shells.

Slide 12

• Electron Affinity (Ea) is the energy change when an electron is added to a neutral gaseous atom to form a negatively charged ion.
• Ea can be expressed using the following equation:
  Ea + e- ⟶ X-
• Ea is typically measured in kilojoules per mole (kJ/mol).

Slide 13

• Similar to the d-block elements, the Electron Affinity of f-block elements also shows a general increasing trend across a period.
• However, there are again exceptions and irregularities within this trend.

Slide 14

• The irregularities in the Electron Affinity trend of f-block elements can be explained by factors such as electron-electron repulsion and subshell stability.
• The stability of half-filled and fully-filled f subshells can affect Electron Affinity values.

Slide 15

• Example of irregularity: Gadolinium (Gd) - Gd has an Electron Affinity value of -41 kJ/mol, which is lower than expected. This is due to the stability of a half-filled f subshell (4f^7).

Slide 16

• The Electron Affinity trends of the f-block elements can be represented on a graph, similar to the d-block elements.
• The curve shows the variations in Electron Affinity values across a period.

Slide 17

• Understanding the Electron Affinity trends of f-block elements helps predict their chemical behavior and reactivity.
• It is particularly important in understanding the formation of coordination complexes and the stability of different oxidation states.

Slide 18

• Example of Electron Affinity in coordination complexes: The transition metal ion in a coordination complex attracts electron-donating ligands due to its high Electron Affinity, leading to the formation of a stable complex.

Slide 19

• Example of Electron Affinity in oxidation states: The stability of different oxidation states of f-block elements is influenced by their Electron Affinity values.
• For example, Cerium (Ce) exhibits multiple oxidation states (-4, +3, +4), with its Electron Affinity playing a role in determining the stability of each oxidation state.

Slide 20

• To summarize:
  • The Electron Affinity of f-block elements generally increases across a period, with exceptions and irregularities due to electron-electron repulsion and subshell stability.
  • Understanding Electron Affinity is crucial in predicting the chemical behavior of f-block elements in coordination complexes and oxidation states.

The f- and d- block elements - Interpretation of Ea curve of d-block

• The d-block elements are located in the middle of the periodic table.
• They are also known as transition metals.
• These elements have partially filled d orbitals in their valence shells.
• Electron Affinity (Ea) is the energy change when an electron is added to a neutral gaseous atom to form a negatively charged ion.
• Ea is typically measured in kilojoules per mole (kJ/mol).

Slide 22

• The Electron Affinity of d-block elements generally increases across a period.
• This is due to the increased effective nuclear charge, which attracts the added electron more strongly.
• However, there are exceptions and irregularities in this trend.
• Repulsion between electrons can lead to a decrease in Electron Affinity.
• Subshell stability, particularly half-filled and fully-filled subshells, can also affect Electron Affinity.

Slide 23

• Example of irregularity: Chromium (Cr) - Cr has an Electron Affinity of -64 kJ/mol, which is lower than expected.
• This is due to the stability of a half-filled d subshell (4s^13d^5).
• Another example of irregularity: Copper (Cu) - Cu has an Electron Affinity of -119 kJ/mol, significantly lower than expected.
• This is also due to the stability of a half-filled d subshell (4s^13d^10).

Slide 24

• The irregularities in the Electron Affinity trend of d-block elements can be explained by factors such as electron-electron repulsion and subshell stability.
• A graph can be plotted to represent the Electron Affinity trend across a period of d-block elements.
• The curve of the Electron Affinity shows the variations in values as we go from left to right in the period.
• Understanding Electron Affinity is important in predicting the chemical behavior and reactivity of d-block elements.

Slide 25

• Electron Affinity also plays a crucial role in the formation of ionic compounds.
• Example: The reaction of Iron (Fe) with oxygen to form Fe2O3 depends on the Electron Affinity of Fe.
• If Fe has a high Electron Affinity, the reaction will be favorable and lead to the formation of the oxide.

Slide 26

• Electron Affinity is also involved in the formation of halides.
• Example: The reaction of Copper (Cu) with Chlorine (Cl) to form CuCl2 depends on the Electron Affinity of Cu.
• If Cu has a high Electron Affinity, the reaction will be favorable and lead to the formation of the halide.

Slide 27

• In summary:
  • The Electron Affinity of d-block elements generally increases across a period, with exceptions and irregularities.
  • Irregularities can be attributed to electron-electron repulsion and subshell stability.
  • Understanding Electron Affinity helps predict chemical behavior and reactivity.
  • It is important in explaining the formation of ionic compounds and halides.

The f- and d- block elements - Interpretation of Ea curve of f-block

• The f-block elements, also known as inner transition metals, are located at the bottom of the periodic table.
• These elements have partially filled f orbitals in their valence shells.
• Electron Affinity (Ea) is the energy change when an electron is added to a neutral gaseous atom to form a negatively charged ion.
• Ea is typically measured in kilojoules per mole (kJ/mol).

Slide 29

• The Electron Affinity of f-block elements generally follows a similar trend to the d-block elements, with an increasing value across a period.
• However, there are exceptions and irregularities within this trend.
• Factors such as electron-electron repulsion and subshell stability can explain these irregularities.

Slide 30

• Example of irregularity: Gadolinium (Gd) - Gd has an Electron Affinity value of -41 kJ/mol, which is lower than expected.
• This is due to the stability of a half-filled f subshell (4f^7).
• Understanding the Electron Affinity trends of f-block elements is important in predicting their chemical behavior and reactivity, particularly in coordination complexes and oxidation states.