An element with 18 protons and 18 neutrons is argon-36, a stable isotope of argon.
What is the name of an element with 18 protons 22 neutrons and 18 electrons?
That element is argon-40, the most abundant isotope of argon found in nature.
Eighteen protons lock it in as argon, no matter what. The 22 neutrons bump its mass number to 40 (18 + 22). Those 18 electrons keep the whole thing electrically balanced. Honestly, this is the isotope you’re mostly breathing right now—argon-40 makes up more than 99% of the argon in air. Because it won’t react with anything, engineers stuff it into light bulbs and welding torches to stop hot metal from turning into rust.
Can chlorine have 18 protons?
No, chlorine cannot have 18 protons—it always has 17 protons.
Chlorine’s atomic number is 17, so every single chlorine atom is born with exactly 17 protons. Shift that to 18 and the atom instantly becomes argon instead. Chlorine does, however, happily carry 18 neutrons in chlorine-35. Protons define the element; neutrons just come along for the ride and create isotopes. That’s why you’ll never meet a chlorine atom with 18 protons.
How many neutrons are in argon 18?
There is no such thing as “argon 18”—argon doesn’t have an isotope labeled by neutron count alone.
You’ll usually see argon isotopes labeled by their mass numbers: argon-36, argon-38, argon-40. Argon-36 gives you 18 neutrons (18 protons plus 18 neutrons). Argon-18 would mean zero neutrons, and that’s physically impossible. So when someone casually says “argon 18,” they almost certainly mean argon-36. Always double-check the mass number—it’s the real neutron-plus-proton total.
What element has 18 as its atomic number?
The element with atomic number 18 is argon (Ar), a noble gas in Group 18 of the periodic table.
Argon sits quietly in the air—colorless, odorless, and stubbornly unreactive—making up roughly 0.93% of the atmosphere. Light-bulb makers love it because it stretches filament life. Window installers use it between panes to cut heat loss. Archivists pump it into display cases to keep old manuscripts from yellowing. Even your old plasma TV owed its blue glow to argon gas getting zapped with electricity.
Alex Chen is a senior tech writer and former IT support specialist with over a decade of experience troubleshooting everything from blue screens to printer jams. He lives in Portland, OR, where he spends his free time building custom PCs and wondering why printer drivers still don't work in 2026.