Final answer:
The atomic masses of any two elements contain the same number of atoms when you have a mass in grams equal to the element's atomic mass, which equates to one mole. One mole of any substance contains Avogadro's number of atoms (6.022 × 10²³). The concept is based on the relationship between the atomic mass unit (amu) and the carbon-12 reference standard.
Step-by-step explanation:
The atomic masses of any two elements contain the same number of atoms. This is because each element's atomic mass given on the periodic table can be used to determine the molar mass of the element in grams per mole (g/mol). According to the molar concept, one mole of any substance contains 6.022 × 10²³ atoms, also known as Avogadro's number. In other words, if you have a substance's mass in grams equal to its atomic mass, that quantity will contain exactly one mole of atoms.
Using carbon-12 (¹²C) as a reference, with an atomic mass of 12 atomic mass units (amu), one mole of ¹²C is equivalent to 12 grams and contains 6.022 × 10²³ atoms of ¹²C. Since the atomic mass of an element is measured relative to carbon-12, the relationship between atomic mass in amu and molar mass in grams holds true for all elements. Therefore, regardless of the element, the molar mass will provide the same number of atoms when you have one mole, or the elemental weight in grams, of that element.