Question

The atomic masses of $Li$ and $K$ are $7$ and $39,$ respectively. According to law of triads the atomic mass of $Na$ will be

• A. $23$
• B. $32$
• C. $46$
• D. $64$

Answer 1

Answer: (A)

Atomic mass of middle element of triad is equal to average of masses of terminal elements.

$Li$ Na $K$

$72339\frac{7+39}{2}=23$