Write the formula for calcium hydride.
Calcium is a Group 2 metal, so Ca2+. Hydride is H-. Two hydrides balance one calcium: CaH2.
Hydrogen Charge: +1 or -1?
Hydrogen commonly forms H+ H- in introductory ionic compounds.
Hydrogen is +1 in almost every compound you meet in a first-year course: HCl, H2O, H2SO4. The exception is metal hydrides such as NaH and CaH2, where hydrogen sits on the metal side of the bond and carries a -1 charge as the hydride ion, H-.
| Element | Hydrogen |
|---|---|
| Symbol | H |
| Atomic number | 1 |
| Common ionic charge | +1, -1 |
| Common ions | H+, H- |
Visual reference
Hydrogen element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
The electron count behind Hydrogen's charge
Hydrogen has a single 1s electron. Losing it gives the bare proton H+, which is what acids donate in solution. But hydrogen is also just one electron short of the filled 1s2 configuration of helium, so when it bonds to a strongly electropositive metal it gains an electron instead and becomes hydride.
The classic Hydrogen error
Students often write hydrogen as -1 in water because it is 'bonded to oxygen.' Direction matters: oxygen is more electronegative, so oxygen takes the electrons and hydrogen stays +1. Hydrogen is only -1 when its partner is a metal less electronegative than itself.
Worked example: H in a formula problem
H+ and H- in real compounds
HCl
Hydrogen chloride
H+ balances chloride ions.
H2O
Hydrogen oxide
Hydrogen can form oxides where total positive and negative charge balances.
Questions students ask about hydrogen
Is hydrogen ever neutral in a compound?
In elemental H2 the oxidation state is 0, but inside compounds hydrogen is assigned +1 (with nonmetals) or -1 (with metals). There is no common compound where it stays 0.
Why does the periodic table sometimes put hydrogen above lithium and above fluorine?
Because it behaves both ways: it forms +1 ions like the alkali metals and -1 ions like the halogens. Its placement is a compromise, not a rule about its charge.
What charge does hydrogen have in NaH?
-1. Sodium must be +1, and the compound is neutral, so hydrogen carries the negative charge. NaH is a classic hydride.
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.