Lanthanum commonly forms La3+ in introductory ionic compounds.
| Element | Lanthanum |
|---|---|
| Symbol | La |
| Atomic number | 57 |
| Common ionic charge | +3 |
| Common ions | La3+ |
Images are used as visual references; charge rules still depend on the compound.
Lanthanum is [Xe]5d1 6s2 — three electrons outside a xenon core, all of which leave to form La3+ (an empty d and f shell, like scandium and yttrium above it). With no f electrons to complicate matters, lanthanum is the cleanest example of the rare-earth +3 rule.
This is a classroom reference range, not an exhaustive list of all oxidation states.
Expecting exotic behavior from an exotic-sounding element. Lanthanum formula problems are aluminum problems in disguise: La2O3, La2(SO4)3, La(OH)3 — cross a fixed 3+ with the anion and you are done.
La3+ with CO3 2- crosses to La2(CO3)3. In the gut, La3+ swaps carbonate for dietary phosphate, forming LaPO4 so insoluble it exits the body — a 3+ ion deployed as a phosphate magnet.
Lanthanum chloride
La3+ balances chloride ions.
Lanthanum oxide
Lanthanum can form oxides where total positive and negative charge balances.
La2O3 raises glass's refractive index with low color distortion — 'lanthanum glass' lets sharp lenses be thinner. The La3+ sits in the glass network as a structural heavyweight.
NiMH battery anodes use LaNi5 alloy (neutral metals) that soaks up hydrogen. A Prius-era pack held over 10 kg of lanthanum — at charge 0, storing H atoms between the metal atoms.
It is the namesake of the lanthanides, and no — it is more abundant in the crust than lead. 'Rare earth' records the historical difficulty of separating these look-alike 3+ ions, not scarcity.
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.
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