Question

In dobereiner's triad containing Li,Na,K if atomic masses of lithium and potassium are 6.9 and 39.1,then what will be the atomic mass of sodium?​

Answer 1

Dobereiner' triad : " The atomic mass of the middle element of triad is the arithmetic mean of the atomic masses of the other two elements. "

In this Question, It is given that if atomic masses of lithium and potassium are 6.9 and 39.1


Here, Atomic mass of Lithium = 6.9

Atomic mass and Potassium = 39.1

Now, Using Dobereiner' triad ,

Arithmetic mean = 39.1 + 6.9 ÷ 2

Sodium= 46/2

Sodium = 23


This, Required Atomic mass of Sodium is 23.

Answer 2

Solution:- In dobereiner's triad containing Li,Na,K if atomic masses of lithium and potassium are 6.9 and 39.1.

Theory used here:-

Dobereiner's law of triads states that, the atomic mass of the middle element of a triad is the arithmetic mean of the atomic masses of the other two elements.

According to dobereiner, average of atomic masses of 1st and 3rd atom.

Atomic mass of Li = 6.9

Atomic mass of K = 39.1

Atomic mass of Na
=6.9+39.1 /2

=46/2 = 23u

Therefore, the atomic mass of Sodium (Na) = 23 u

[Answer: 23 u]