Look up an element by symbol, name, or atomic number, then use its atomic weight to convert grams into moles and approximate atom count. Use it to test different inputs quickly, compare outcomes, and understand the main factors behind the result before moving on to related tools or deeper guidance.
Last updated
Look up an element, then add grams if you need moles Search by symbol, full name, or atomic number to retrieve the standard atomic weight. If you also
enter a sample mass, the worksheet converts that gram amount into moles and an approximate atom count.
Enter an element to begin Use a symbol like Fe, a name like Iron, or an atomic number like 26 to load the lookup result.
Element weights lookup guide: atomic weights, grams-to-moles conversion, and atom counts
An element-weight lookup is most useful when it does more than display a number from the periodic table. This page lets you search an element by symbol, name, or atomic number, then use the listed atomic weight to convert a gram amount into moles and an approximate atom count.
What an element-weight lookup should tell you
Atomic weight is the periodic-table value used for routine element mass calculations. For a lookup tool to be practical, it should not stop at the element name and symbol. It should also tell you the atomic number, broad chemical family, and the standard atomic-weight value you would actually use in introductory chemistry work.
That is why this page treats lookup as the start of a calculation workflow. Once an element is identified, the same result can support grams-to-moles conversion and an approximate atom count without sending you to a second tool.
How the gram-to-mole conversion works
The listed atomic weight is used as the molar mass for the elemental substance in grams per mole. Once you know that value, converting a measured mass into amount of substance is a direct division: grams divided by atomic weight gives moles.
If you also want an atom count, multiply the mole amount by Avogadro's number. This is the same counting relationship used throughout chemistry: one mole corresponds to 6.022 × 10²³ atoms, molecules, or formula units depending on the substance under discussion.
moles = mass (g) / atomic weight (g/mol)
Converts the entered gram amount into amount of substance for the selected element.
atoms = moles × 6.022 × 10²³
Uses Avogadro's number to estimate how many atoms are present in that sample.
Worked example: iron
Suppose you look up iron and enter 55.84 g. The page shows an atomic weight of 55.84 g/mol, so the sample corresponds to 1 mole of iron atoms.
That same result means the sample contains approximately 6.022 × 10²³ iron atoms. If you instead entered 27.92 g, the mole amount would be about 0.5 mol and the atom count would be about half of Avogadro's number.
What this lookup does not cover
This page uses standard atomic-weight values for elemental lookups. It does not replace isotope-specific mass tables, mass-spectrometry data, or full compound stoichiometry tools.
Use it for periodic-table reference, classroom conversions, and quick elemental mass work. For molecular formulas, isotopic composition, or reaction stoichiometry, use a dedicated chemistry calculator built for those tasks.
Further reading
PubChem periodic table — NIH-hosted periodic table reference covering atomic numbers, masses, and broad element properties.
NIST Chemistry WebBook — NIST chemistry reference used for deeper property and substance lookups beyond the periodic-table summary level.
Frequently asked questions
Is atomic weight the same as molar mass for an element?
For routine chemistry calculations, yes. The atomic-weight value from the periodic table is used numerically as the molar mass in grams per mole for the elemental substance.
Why is the atom count only approximate?
Because standard atomic weights are average values that reflect natural isotopic abundance. The counting conversion is still the correct chemistry relationship, but the displayed atom total is an estimate based on the listed average mass value.
Can I use this page for compounds like H2O or NaCl?
No. This lookup is for individual elements only. For compounds, use a molar-mass or chemical-compound calculator that adds the atomic contributions from every element in the formula.
Why do some heavy elements have expected states rather than ordinary labels?
For some superheavy elements, the standard state at ordinary conditions is predicted from theory rather than established from macroscopic bulk samples. The lookup preserves that reference wording instead of overstating certainty.
