Definition

1. Noun:
   • A specific quantity of a chemical element: A "gram atom" is the amount of an element that has a mass in grams numerically equal to its atomic weight. It represents a fixed number of atoms of that element, known as Avogadro's number (approximately 6.022 × 10²³ atoms).

Usage Examples

• Noun:
  • One gram atom of carbon-12 has a mass of exactly 12 grams.
  • The experiment required precisely one gram atom of the metal.
  • The concept of a gram atom is foundational for understanding the mole in chemistry.

Advanced Usage

• Historical Context: The term "gram atom" is largely historical and has been superseded in modern scientific usage by the mole. One mole of atoms of an element is equivalent to one gram atom of that element.
  • While "gram atom" is an older term, it helped bridge the gap between atomic mass and measurable quantities.

Variants and Related Words

• Mole (n): The modern SI base unit for amount of substance. One mole contains exactly 6.02214076×10²³ elementary entities (atoms, molecules, etc.).
  • One mole of oxygen atoms is equivalent to one gram atom of oxygen.
• Atomic Weight (n): The average mass of atoms of an element, measured in atomic mass units (amu). It is the numerical value used to determine the mass of a gram atom.
  • The atomic weight of iron is about 55.85, so one gram atom of iron has a mass of about 55.85 grams.

Synonyms

• Gram-atomic weight: This is a direct synonym, emphasizing it is a weight in grams.
• Mole of atoms: A more modern and precise synonym for the same quantity of substance.

Notes on Meaning

• The term specifically refers to elements, not compounds. For a compound, the analogous historical term is "gram molecule" or "gram formula weight."
• The numerical value is based on the relative atomic weight (a dimensionless number) from the periodic table. Therefore, a gram atom of different elements will have different masses but contain the same number of atoms.

Noun

1. the quantity of an element whose weight in grams is numerically equal to the atomic weight of the element