Atomic weight al

Al is the chemical symbol for aluminum, also called aluminium. Its standard atomic-weight value is about 26.98 in many introductory tables, corresponding to a molar mass near 26.98 g/mol for aluminum atoms.

Meaning and context

Atomic weight is a relative quantity, while molar mass expresses mass per amount of substance. Their numerical values are closely connected in the familiar gram-per-mole convention, but the terms and units describe different quantities.

Examples and usage

For Al₂O₃, count two aluminum atoms and three oxygen atoms. Using rounded values of 26.98 and 16.00 gives 2×26.98 + 3×16.00 = 101.96 g/mol. The subscripts multiply each element’s contribution.

What to check

Use the values provided by the course or reference table consistently. Do not round intermediate contributions more aggressively than necessary. An alloy containing aluminum has a composition different from a pure-element sample, so a single elemental value does not characterize the whole alloy.

Explore more: Chemistry and Elements