Periodic table element lookup
Find an element by name, symbol or atomic number, with its weight, group, block and electron configuration.
A clear answer. Here’s how.
Matches an atomic number, symbol or name exactly, ignoring case and a few older names such as wolfram, then falls back to names that start with your search. Standard atomic weights are the IUPAC conventional values to the digits shown; elements with no standard value show the mass number of their longest-lived isotope in brackets. Period, group and block follow from the atomic number in the 18-column table. Ground-state electron configurations fill subshells in the order 1s 2s 2p 3s 3p 4s 3d … with the measured exceptions (such as chromium and copper); configurations beyond lawrencium are predictions.
How this is checked
4 reference checks passed These 4 cases were run when this page was built, on 20 October 2026, and all reproduce within the stated tolerance. The same cases are part of the automated tests that run on every change to Toolmoz. Engine version 1.
See the checks and where each expected answer comes from
Case 1
- Inputs
- Element name, symbol or atomic number Fe
- Expected, and what Toolmoz gave
- Name expected Iron, Toolmoz IronAtomic number (protons) expected 26, Toolmoz 26Standard atomic weight (conventional, g/mol) expected 55.845, Toolmoz 55.845Period (row) expected 4, Toolmoz 4Group (column) expected 8, Toolmoz 8Block expected d, Toolmoz dGround-state electron configuration expected [Ar] 3d⁶ 4s², Toolmoz [Ar] 3d⁶ 4s²
- Where the expected answer comes from
- Iron is element 26, 55.845 g/mol (CIAAW abridged), period 4, group 8, d-block, [Ar] 3d⁶ 4s² (NIST)
- Allowed difference
- exact
Case 2
- Inputs
- Element name, symbol or atomic number copper
- Expected, and what Toolmoz gave
- Name expected Copper, Toolmoz CopperSymbol expected Cu, Toolmoz CuAtomic number (protons) expected 29, Toolmoz 29Ground-state electron configuration expected [Ar] 3d¹⁰ 4s¹, Toolmoz [Ar] 3d¹⁰ 4s¹
- Where the expected answer comes from
- Copper is element 29, and its ground state is the well-known 3d¹⁰ 4s¹ exception to the filling order (NIST)
- Allowed difference
- exact
Case 3
- Inputs
- Element name, symbol or atomic number 79
- Expected, and what Toolmoz gave
- Name expected Gold, Toolmoz GoldSymbol expected Au, Toolmoz AuGroup (column) expected 11, Toolmoz 11Ground-state electron configuration expected [Xe] 4f¹⁴ 5d¹⁰ 6s¹, Toolmoz [Xe] 4f¹⁴ 5d¹⁰ 6s¹
- Where the expected answer comes from
- Gold is element 79 in group 11 with [Xe] 4f¹⁴ 5d¹⁰ 6s¹ (NIST)
- Allowed difference
- exact
Case 4
- Inputs
- Element name, symbol or atomic number neon
- Expected, and what Toolmoz gave
- Symbol expected Ne, Toolmoz NeGroup (column) expected 18, Toolmoz 18Category expected Noble gas, Toolmoz Noble gasState at 20 °C and 1 atm expected Gas, Toolmoz GasGround-state electron configuration expected [He] 2s² 2p⁶, Toolmoz [He] 2s² 2p⁶
- Where the expected answer comes from
- Neon is a group 18 noble gas, gaseous at room temperature, with a full 2s² 2p⁶ shell
- Allowed difference
- exact
What this shows: the engine reproduces independently worked values for these cases. It does not prove every possible input is right. To test an answer you were given, see how to check a number; to see what is and is not checked across Toolmoz, see the accuracy ledger.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Element name, symbol or atomic number
- Fe
Example result
- Name
- Iron
- Symbol
- Fe
- Atomic number (protons)
- 26
- Standard atomic weight (conventional, g/mol)
- 55.845
- Period (row)
- 4
- Group (column)
- 8
- Block
- d
- Category
- Transition metal
- State at 20 °C and 1 atm
- Solid
- Ground-state electron configuration
- [Ar] 3d⁶ 4s²
Weights are IUPAC conventional values to the digits shown (abridged); real samples vary. Configurations are measured ground states up to lawrencium and predicted beyond. Groups follow the 18-column table, lanthanides and actinides are shown outside numbered groups, and category boundaries differ between textbooks.