Question

The atomic mass of Lithium is 7 and the atomic mass of Potassium is 39. The average masses of Lithium and Potassium gave the atomic mass of Sodium which is 23. Which law gives such type of an arrangement?
1. Avogadro Law
2. Newland’s law of octaves
3. Mendeleev’s law
4. Dobereiner’s law of triads

Answer 1

Correct Answer - Option 4 : Dobereiner’s law of triads

The correct answer is Dobereiner’s law of triads.

• Dobereiner’s law of triads:
  • Dobereiner’s law of triads states that when elements are arranged in the order of increasing atomic masses, the atomic mass of the middle element of the triad is approximately the average of the atomic masses of the other two elements.
  • Example: 
    • In the triad of Lithium, Sodium, and Potassium, the atomic mass of Lithium is 7 and the atomic mass of Potassium is 39. The average masses of Lithium and Potassium give the atomic mass of Sodium 23. 

• Avogadro Law:
  • It states that equal volumes of different gases will contain equal numbers of molecules under the same conditions of temperature and pressure.
• Newland’s law of octaves: 
  • It states that when elements are arranged in order to increase atomic masses, every eighth element has properties similar to the first.
• Mendeleev’s law:
  • The law states that the physical and chemical properties of the elements are the periodic function of their atomic masses.