Write the formula for barium hydroxide, one of the few strong soluble bases outside Group 1.
Ba2+ with two OH-: Ba(OH)2. Its solutions absorb CO2 so avidly (forming cloudy BaCO3) that it serves as the classic carbon-dioxide test reagent.
What Is the Charge of Barium?
Barium commonly forms Ba2+ in introductory ionic compounds.
Barium is 2+ in every compound: BaSO4 (the 'barium meal' of X-ray imaging), BaCl2, green-burning Ba(NO3)2 in fireworks. Group 2 position, one possible charge, zero exceptions.
| Element | Barium |
|---|---|
| Symbol | Ba |
| Atomic number | 56 |
| Common ionic charge | +2 |
| Common ions | Ba2+ |
Visual reference
Barium element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Why Barium lets go of two electrons
Barium is [Xe]6s2. Two 6s electrons leave readily (503 and 965 kJ/mol); the third would breach the xenon core at 3,600 kJ/mol, which chemistry never funds. Its low charge density — a big ion with only 2+ — also explains its salts' distinctive solubility habits.
Where Barium formulas usually go wrong
Worrying that the 'barium swallow' poisons patients, since Ba2+ is genuinely toxic. The trick is solubility: BaSO4 is so insoluble (about 2 mg per liter) that essentially no free Ba2+ enters the body — the sulfate lattice keeps its barium locked. Soluble BaCl2, by contrast, is dangerous.
Worked example: Ba in a formula problem
Ba2+ in real compounds
BaCl2
Barium chloride
Ba2+ balances chloride ions.
BaO
Barium oxide
Barium can form oxides where total positive and negative charge balances.
Questions students ask about barium
Why does barium burn green in fireworks?
In the flame, transient BaCl and BaOH molecules emit at ~510-530 nm. The 2+ ion itself is colorless; pyrotechnic green belongs to those short-lived molecular species.
How does the sulfate test use barium's charge?
Add BaCl2 to a solution: a white precipitate that ignores added acid means sulfate — the 2+/2- pairing of BaSO4 is insoluble beyond nearly everything else in the qualitative-analysis toolbox.
Is barium's +2 related to why X-rays image it so well?
Indirectly: imaging contrast comes from barium's 56 electrons stopping X-rays, and the charge story (insoluble +2 sulfate) is what makes it safe to hold that heavy atom inside the gut.
How do I use this charge in formulas?
Combine positive and negative ions so the total charge is zero — or let the ionic compound calculator do the crossing for you. The full chart lives on the periodic table with charges.
Where this data comes from
Charges and element facts on this page are checked against the primary references below. Found an error? Email hello@periodictablewithcharges.com — corrections ship in the next content update. See how this site is edited.