The number of atoms in exactly 12 g of carbon-12 is known as:

Correct option is A

​The correct answer is (a) Avogadro’s constant

Explanation:

The number of atoms in exactly 12 grams of carbon-12 is known as Avogadro’s constant.

• Avogadro's constant (also called Avogadro's number) is the number of constituent particles (atoms, molecules, ions, etc.) present in one mole of a substance.
• It is approximately 6.022 × 10²³ particles per mole.
• For carbon-12, 12 grams represents exactly one mole, which contains 6.022 × 10²³ atoms.

Thus, the correct answer is Avogadro’s constant.

Information Booster:

Avogadro’s Constant:

• Definition: The number of particles (atoms, molecules, ions, etc.) in one mole of a substance.
• Value: Approximately 6.022 × 10²³ particles/mole.
• Importance in Chemistry: It allows chemists to count particles by weighing a substance, and it provides a bridge between the atomic scale and the macroscopic scale.
• Unit: Mole (mol) is the unit of amount of substance in the International System of Units (SI).

Example:

• One mole of carbon-12 weighs 12 grams and contains 6.022 × 10²³ atoms.

Additional Knowledge:

• Rydberg constant: The Rydberg constant is related to the wavelengths of spectral lines of hydrogen and is used in the Rydberg formula to predict the wavelengths of the lines in the hydrogen spectrum.

• Planck’s constant: Planck’s constant (denoted as h) relates the energy of a photon to its frequency and is fundamental in the field of quantum mechanics. Its value is approximately 6.626 × 10⁻³⁴ J·s.

• Faraday’s constant Faraday's constant (denoted as F) is the magnitude of electric charge per mole of electrons, approximately 96,485 C/mol. It is important in electrochemistry.