Argon (Ar)
Argon makes up about 0.93% of Earth's atmosphere, making it the third most abundant gas in dry air after nitrogen and oxygen.
Argon properties
- Atomic mass
- 39.948 u
- Category
- Noble gas
- Group
- 18
- Period
- 3
- Block
- p-block
- Melting point
- 83.81 K (-189.3 °C)
- Boiling point
- 87.3 K (-185.8 °C)
- Density
- 1.784 g/L
- Atomic radius
- 188 pm
- Ionization energy
- 15.76 eV
- Electron affinity
- —
- Radioactive
- No, has stable isotopes
- Discovered
- 1894
Argon electron configuration
- Electron configuration
- [Ne] 3s2 3p6
- Full electron configuration
- 1s2 2s2 2p6 3s2 3p6
- Electron shells
- 2 · 8 · 8
The electron configuration of Argon (Ar) is [Ne] 3s2 3p6. Its 18 electrons are arranged in shells as 2, 8, 8.
Protons, neutrons and electrons in Argon
A neutral Argon atom has 18 protons and 18 electrons. Most Argon atoms have about 22 neutrons: the atomic mass rounded to 40, minus the atomic number 18.
Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass
How many valence electrons does Argon have?
8
Argon has 8 valence electrons in its outermost shell, shell 3. These are the electrons involved in chemical bonding.
Argon orbital diagram
Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations
Molar mass of Argon
39.948 g/mol
One mole of Argon atoms (6.022 × 10²³ atoms) has a mass of 39.948 grams. Use this value to convert between grams and moles.
Argon facts
- Argon makes up about 0.93% of Earth's atmosphere, making it the third most abundant gas in dry air after nitrogen and oxygen.
- Argon's name comes from the Greek argos, meaning 'lazy' or 'idle', because it would not react with anything.
- Argon (Ar) has atomic number 18 and is a gas at room temperature. It was discovered in 1894.
Position in the periodic table
Argon is element 18, in period 3 and group 18 of the periodic table, in the p-block.
Uses of Argon
Argon is widely used as a shielding gas in welding, where it keeps oxygen and moisture away from the hot metal. It fills incandescent light bulbs to slow the evaporation of the glowing filament, and it fills the gap between the panes of many energy-efficient windows. Steelmakers and producers of silicon crystals and titanium also use argon to provide an unreactive atmosphere.
Who discovered Argon?
Lord Rayleigh and William Ramsay discovered argon in 1894 in London, after noticing that nitrogen taken from air was slightly denser than nitrogen made from chemical compounds. They removed the nitrogen and oxygen from a sample of air and found an unreactive gas left behind.
Where does the name come from?
Argon comes from the Greek argos, meaning 'idle' or 'lazy'. Its discoverers chose the name in 1894 because the gas refused to react with any of the substances they tried.
Same group
Compare Argon
FAQ
What is the electron configuration of Argon?
The electron configuration of Argon (Ar) is [Ne] 3s2 3p6. Its 18 electrons are arranged in shells as 2, 8, 8.
How many protons, neutrons and electrons does Argon have?
A neutral Argon atom has 18 protons and 18 electrons. Most Argon atoms have about 22 neutrons: the atomic mass rounded to 40, minus the atomic number 18.
How many valence electrons does Argon have?
Argon has 8 valence electrons in its outermost shell, shell 3. These are the electrons involved in chemical bonding.
What is the molar mass of Argon?
The molar mass of Argon is 39.948 g/mol. This is the same number as its atomic mass, 39.948 u.
Is Argon a metal?
No. Argon is a noble gas, so it is a nonmetal.
Is Argon radioactive?
Ordinary Argon is not radioactive: it has at least one stable isotope. Like every element, it also has radioactive isotopes, most of them made in laboratories.
Where is Argon on the periodic table?
Argon is element 18, in period 3 and group 18 of the periodic table, in the p-block.