Question

The plot of square root of frequency of $X$-ray emitted against atomic number led to suggestion of which law/rule ?

• A. Periodic law
• B. Modern periodic law
• C. Hund’s rule
• D. Newland’s law

Answer 1

Answer: (B)

Moseley, gave modern periodic law. He showed that atomic number is more fundamental property of an element than its atomic mass as follows

"The square root of the frequency of a line (of X-ray spectrum) is related to the atomic number $Z$ of the target material as,

$\sqrt{v}=a(Z-b)$

where, $a=$ proportionality constant

$Z=$ atomic number

$b=$ another constant

$L$ it, has the same value for all the lines of X-rays spectrum).