Periodic Trends

Ionization Energy

What does it cost to steal an electron?

⏱ — min read

Imagine an atom — a tiny world with a nucleus at its core and electrons buzzing around it. Ionization energy is the “energy cost” to pluck the most loosely held electron from a gaseous atom in its ground state.

Think of it as how strongly the atom holds onto its outermost electron. High ionization energy → tight grip. Low ionization energy → easy to snatch away. On the periodic table, ionization energy generally increases across a period and decreases down a group.

Photoelectron spectroscopy (PES)

Atoms in the gas phase are exposed to high-energy ultraviolet or X-ray photons. When a photon hits an atom with enough energy, it ejects an electron. The spectrometer measures the kinetic energy of the ejected electron:

Ionization Energy = Energy of Photon − Kinetic Energy of Ejected Electron

This method is precise enough to determine ionization energies of individual orbitals.

First, Second, Third…

Removing the first electron is IE₁. The second removal is harder because you’re pulling from a positively charged ion. Huge jumps occur when you start tearing into a noble-gas core — those electrons are deeply held. Successive ionization energies reveal electron-shell structure.

Semiconductors

In silicon and germanium, ionization energy determines how easily electrons can be excited to conduct electricity — the foundation of modern electronics.

Batteries

Elements like lithium with low ionization energies readily lose electrons, making them ideal for storing and releasing energy efficiently.

Corrosion resistance

Gold and platinum have high ionization energies, so they don’t lose electrons easily and remain stable in harsh environments.

Catalysis

Transition metals with moderate ionization energies act as excellent catalysts by easily exchanging electrons — vital for fuel cells and industrial synthesis.

// periodic table dashboard

Trends Across the Table

Groupwise Analysis

Select Group

💡Tip: Click any bar to see the full IE₁–IE₇ progression for that element

Trend Analysis

Loading…

Element — Successive Ionization Energies

Note: First ionization energy (IE₁) is shown in the main chart. Click any bar to drill down and view IE₁–IE₇ for that element on a logarithmic scale, revealing shell-boundary jumps highlighted in red.

References:

Kramida A. et al., NIST ASD Team. NIST Atomic Spectra Database Ionization Energies Data (ver. 5.11), 2023. physics.nist.gov/asd

Periodwise Analysis

Select Period

💡Tip: Click any bar to see the full IE₁–IE₇ progression for that element

Trend Analysis

Loading…

Element — Successive Ionization Energies

Note: IE₁ is shown in the main chart. Click any bar for IE₁–IE₇ drill-down on a logarithmic scale.

References:

NIST Atomic Spectra Database (ver. 5.11)

Transition Metals Analysis

Select Series

💡Tip: Click any bar to see the full IE₁–IE₇ progression for that element

Trend Analysis

Loading…

Element — Successive Ionization Energies

Note: IE₁ is shown in the main chart. Click any bar for IE₁–IE₇ drill-down on a logarithmic scale.

References:

NIST Atomic Spectra Database

Lanthanide / Actinide Analysis

Select Series

💡Tip: Click any bar to see the full IE₁–IE₇ progression for that element

Trend Analysis

Loading…

Element — Successive Ionization Energies

Note: IE₁ is shown in the main chart. Click any bar for IE₁–IE₇ drill-down.

References:

Lang P. F. & Smith B. C., Ionization Energies of Lanthanides
NIST Atomic Spectra Database (ver. 5.11)