Question

if atomic mass of lithium and potassium are 7 and 39 respectively,what would mass of sodium​

Answer 1

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Dobereiner arranged the elements in increasing order of atomic masses. He found that the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when they are arranged in their increasing order of atomic mass.

So Li=7,K=39

Atomic mass of Na =$\frac{7 + 39}{2} = \frac{46}{2} = 23$

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Answer 2

Explanation:

Lithiums 's Atomic mass=7

Potassium 's Atomic mass=39

According to Duberiner 's tripod theory

Sodium 's Atomic mass = nearable to the average mass of potassium and lithium

$\longrightarrow\sf =\dfrac {39+7}{2}$

$\longrightarrow\sf =\dfrac {46}{2}$

$\longrightarrow\sf =23$