Electron Gain Enthalpy
Why do some atoms love electrons more than others?
Imagine an atom being offered an extra electron. Some atoms eagerly accept it, while others refuse. The energy change that occurs when an atom accepts an electron is called electron gain enthalpy.
When an isolated gaseous atom gains an electron, the process can be represented as:
X(g) + e− → X−(g)
Electron gain enthalpy is the enthalpy change associated with this process.
What does the sign tell us?
Energy is released when the electron is accepted. The atom has a strong attraction for electrons.
Energy must be supplied for the atom to accept an electron. The atom does not readily attract electrons.
Example: Fluorine
F(g) + e− → F−(g)
Fluorine releases a large amount of energy when it gains an electron, so its electron gain enthalpy is highly negative. This shows that fluorine strongly attracts electrons.
Noble gases
Noble gases such as helium already have stable electronic configurations. They do not readily accept additional electrons, resulting in positive electron gain enthalpy values.
Electron gain enthalpy and electron affinity are closely related and are often confused.
| Electron Gain Enthalpy | Electron Affinity |
|---|---|
| Enthalpy change when an electron is gained | Energy released when an electron is gained |
| Usually expressed in kJ mol−1 | Expressed in kJ mol−1 or eV |
| Negative for exothermic processes | Positive when energy is released |
- Electron affinity tells us how much energy is released.
- Electron gain enthalpy tells us the enthalpy change of the same process.
At first glance this may seem like a textbook-only concept. In reality it plays an important role in designing the batteries that power our phones, laptops, and electric vehicles.
A battery works because electrons move from one material to another:
The cathode material must have a strong tendency to accept electrons. The more negative the electron gain enthalpy:
- Easier electron acceptance
- Stronger oxidizing ability
- Higher possible battery voltage
Fluoride-Ion Batteries
F(g) + e− → F−(g)
Fluorine is one of the strongest electron-accepting elements. Because it readily gains electrons, scientists are exploring fluoride-ion batteries and metal-fluoride cathodes as next-generation energy storage systems. These batteries could potentially provide:
How AI Helps Build Better Batteries
Testing thousands of battery materials experimentally is expensive and time-consuming. Today, scientists use AI and quantum chemistry to predict which materials are most likely to work.
Instead of testing 10,000 materials in the laboratory, researchers may only need to test the most promising 10–20 candidates identified through computer simulations.
Trends Across the Table
Groupwise Analysis
Trend Analysis
Loading…- William M. Haynes, CRC Handbook of Chemistry and Physics, 95th ed., CRC Press, 2014
- Kaye & Laby tables of physical & chemical constants (2017)
- Royal Society of Chemistry — interactive periodic table
Periodwise Analysis
Trend Analysis
Loading…- CRC Handbook of Chemistry and Physics, 95th ed.
Transition Metals Analysis
Trend Analysis
Loading…- CRC Handbook of Chemistry and Physics, 95th ed.
Lanthanide / Actinide Analysis
Trend Analysis
Loading…- CRC Handbook of Chemistry and Physics, 95th ed.