This chart ranks elements by first ionization energy, the energy in kilojoules per mole needed to remove one electron from a neutral gaseous atom. Higher values mean the atom holds its electrons more tightly. Helium leads.

About: Elements With the Highest First Ionization Energy

Overview of the data behind this chart

AI Insight

Helium requires the most energy to ionize, 2,372 kJ/mol, because its two electrons occupy a compact, fully filled shell tightly bound to the nucleus. Neon (2,081) follows, and the pattern is clear: noble gases dominate the top of the list thanks to their exceptionally stable electron configurations. Fluorine (1,681) is the highest non-noble-gas element, consistent with its record electronegativity. The values put the periodic law on display, ionization energy generally rises across a period and falls down a group, which is why light elements like helium, neon and fluorine outrank heavier ones such as krypton and xenon. Even hydrogen, with a single electron, needs 1,312 kJ/mol, more than chlorine, underscoring how tightly the smallest atoms bind their electrons.

Data source: Ionization energies of the elements

Key Findings

Auto-computed highlights from this dataset

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Helium leads with 2,372 in All Time.

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Average value in All Time: 1,546 · median: 1,377.

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Gap in All Time: Helium is 2× larger than Xenon.

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Elements With the Highest First Ionization Energy

Data Insights Below

Data Insights

Numbers, trends & sources behind this chart

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Data Points

10 categories · 1 year

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Top Value

2,372.30

Helium

First Ionization Energy (kJ/mol) · All Time

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Metrics

First Ionization Energy (kJ/mol)

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Period

All Time

Single year snapshot

Category Rankings

First Ionization Energy (kJ/mol) · All Time

#	Category	All Time
🥇	Helium	2,372.30
🥈	Neon	2,080.70
🥉	Fluorine	1,681
4	Argon	1,520.60
5	Nitrogen	1,402.30
6	Krypton	1,350.80
7	Oxygen	1,313.90
8	Hydrogen	1,312
9	Chlorine	1,251.20
10	Xenon	1,170.40

Statistical Summary — First Ionization Energy (kJ/mol) · All Time

2,372.30

Maximum

1,170.40

Minimum

1,546

Average

1,377

Median

What This Data Shows

Auto-generated trend summaries per category

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Helium

Recorded 2,372.30 First Ionization Energy (kJ/mol) in All Time.

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Neon

Recorded 2,080.70 First Ionization Energy (kJ/mol) in All Time.

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Fluorine

Recorded 1,681 First Ionization Energy (kJ/mol) in All Time.

Source

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Argon

Recorded 1,520.60 First Ionization Energy (kJ/mol) in All Time.

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Nitrogen

Recorded 1,402.30 First Ionization Energy (kJ/mol) in All Time.

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Krypton

Recorded 1,350.80 First Ionization Energy (kJ/mol) in All Time.

Source

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Oxygen

Recorded 1,313.90 First Ionization Energy (kJ/mol) in All Time.

Source

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Hydrogen

Recorded 1,312 First Ionization Energy (kJ/mol) in All Time.

Source

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Chlorine

Recorded 1,251.20 First Ionization Energy (kJ/mol) in All Time.

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Xenon

Recorded 1,170.40 First Ionization Energy (kJ/mol) in All Time.

Source

Full Data Table

10 records across 1 year

10 sourced

Category	Metric	All Time
Helium	First Ionization Energy (kJ/mol)	2,372.30
Neon	First Ionization Energy (kJ/mol)	2,080.70
Fluorine	First Ionization Energy (kJ/mol)	1,681
Argon	First Ionization Energy (kJ/mol)	1,520.60
Nitrogen	First Ionization Energy (kJ/mol)	1,402.30
Krypton	First Ionization Energy (kJ/mol)	1,350.80
Oxygen	First Ionization Energy (kJ/mol)	1,313.90
Hydrogen	First Ionization Energy (kJ/mol)	1,312
Chlorine	First Ionization Energy (kJ/mol)	1,251.20
Xenon	First Ionization Energy (kJ/mol)	1,170.40