When calculating the formula masses for gaseous elements like hydrogen, nitrogen, and neon, the terms "atomic weight" and "molecular weight" have slightly different meanings.
Atomic weight: The atomic weight, also known as atomic mass, refers to the average mass of the atoms of a specific element. It takes into account the naturally occurring isotopes and their relative abundances. The atomic weight is listed on the periodic table and is expressed in atomic mass units (amu). For example, the atomic weight of hydrogen is approximately 1.008 amu, nitrogen is approximately 14.007 amu, and neon is approximately 20.180 amu.
Molecular weight: The molecular weight, also called the molar mass, is the mass of one mole of a substance. In the case of gaseous elements, the term "molecular weight" might not be commonly used since these elements typically exist as individual atoms rather than molecules in their elemental state. However, the molar mass is still applicable, representing the mass of one mole of atoms. The molar mass of an element is numerically equal to its atomic weight expressed in grams. For example, the molar mass of hydrogen is approximately 1.008 grams/mol, nitrogen is approximately 14.007 grams/mol, and neon is approximately 20.180 grams/mol.
In summary, for gaseous elements like hydrogen, nitrogen, and neon, the atomic weight represents the average mass of the individual atoms, whereas the molecular weight (or molar mass) represents the mass of one mole of atoms. Since these elements exist as individual atoms, the terms "molecular weight" and "molar mass" are often used interchangeably in this context.