Write the formula for strontium nitrate, the fireworks oxidizer-colorant.
Sr2+ with NO3- requires two nitrates: Sr(NO3)2. In the flame, strontium's electrons emit at ~650 nm — the deepest red in pyrotechnics.
What Is the Charge of Strontium?
Strontium commonly forms Sr2+ in introductory ionic compounds.
Strontium is 2+ in every compound: SrCl2, SrCO3, SrSO4. Sr2+ salts paint fireworks crimson, and because Sr2+ so closely resembles Ca2+, bones absorb it — for better (osteoporosis drugs) and worse (fallout strontium-90).
| Element | Strontium |
|---|---|
| Symbol | Sr |
| Atomic number | 38 |
| Common ionic charge | +2 |
| Common ions | Sr2+ |
Visual reference
Strontium element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Why Strontium lets go of two electrons
Strontium is [Kr]5s2, a Group 2 script: two 5s electrons leave, the krypton core stays sealed. The third ionization energy (4,138 kJ/mol) guarantees no Sr3+ ever forms; the comfortable first two guarantee no strontium compound stops at 1+.
Where Strontium formulas usually go wrong
Confusing strontium's chemical charge with its isotope hazards. Stable Sr-88 in fireworks and toothpaste is harmless 2+ chemistry; radioactive Sr-90 from nuclear fallout is dangerous because that same 2+ chemistry files it into bone next to calcium.
Worked example: Sr in a formula problem
Sr2+ in real compounds
SrCl2
Strontium chloride
Sr2+ balances chloride ions.
SrO
Strontium oxide
Strontium can form oxides where total positive and negative charge balances.
Questions students ask about strontium
Why do sensitivity toothpastes contain strontium?
SrCl2 supplies Sr2+ that plugs the exposed micro-channels in dentin, mimicking calcium closely enough to block the fluid movement that triggers pain.
How similar are Sr2+ and Ca2+ really?
Same charge, radii 118 vs 100 pm — close enough that bone-building enzymes accept either. That substitution chemistry is the entire story of strontium in medicine and in fallout.
What made 'glow in the dark' switch to strontium aluminate?
SrAl2O4 doped with europium glows for hours, replacing older zinc sulfide. Strontium's role is structural — its reliable 2+ builds the host crystal; the europium ions do the glowing.
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.