मोज़ले का नियम इस नियमानुसार एक्स किरण स्पेक्ट्रम में किसी स्पेक्ट्रमी रेखा की आवृत्ति (frequency), जिस तत्व से एक्स किरण उत्सर्जित होती है, उसके परमाणु क्रमांक (atomic number) के वर्ग के समानुपाती होती है। यदि एक्स किरण स्पेक्ट्रम में स्पेक्ट्रमी रेखा की आवृत्ति (𝜈) तथा जिस तत्व से एक्स किरण उत्सर्जित होती है उसका परमाणु क्रमांक (Z) हो, तो 𝜈 = Z 2 ⇒ √𝜈 ∝ Z या √𝜈 = a (Z – b ) यहां (Z – b ) एक्स किरण उत्सर्जित करने वाले तत्व का प्रभावी परमाणु क्रमांक तथा b अभिलाक्षणिक नियतांक या आवरणांक है। मोज़ले नियम की उपयोगिता किसी तत्व के अभिलाक्षणिक गुण उसके परमाणु क्रमांक पर निर्भर करते हैं, द्रव्यमान पर नहीं। इसलिए आवर्त सारणी में कुछ तत्वों की स्थिति पुर्नव्यवस्थित की गई। आवर्त सारणी के कुछ नए तत्वों की खोज की गई। जैसे Hf (72), In (61), Re (75) आदि। बोहर सिद्धान्त के आधार पर मोज़ले नियम की व्याख्या n 1 तथा n 2 कोश में इलेक्ट्राॅन की ऊर्जा चूंकि धनात्मक नाभिक अन्य इलेक्ट्राॅनों द्वारा ढक दिया जाता है। इसलिए ह...

Moseley’s law According to it, the frequency of a spectral line in X-ray spectrum varies as the square of the atomic number of the element emitting it. If 𝜈 is the frequency of spectral line in X-ray spectra and Z is the atomic number of element, then 𝜈 = Z 2 ⇒ √𝜈 ∝ Z or √𝜈 = a (Z – b ) Here (Z – b ) is the effective atomic number of emitting element and b is the characteristic constant or screening constant. Importance of Moseley’s law The characteristic property of an element depends on their atomic number, not on their masses. So the position of some elements in periodic table was rearranged. On the basis of Moseley law some new elements of periodic table was discovered like Hf (72), In (61), Re (75) etc. Explanation of Moseley’s law on the basis of Bohr’s theory The energy of electron in n 1 and n 2 orbits are given by Since the positive nucleus is screened by rest of the electrons. Therefore we...

X-ray spectra X-rays X-rays were discovered by a German physicist Wihelm Conrad Roentgen in 1895 during the study of the properties of cathode rays. These rays are actually electromagnetic rays of lower wavelengths having range from 10 Å to 0.5 Å. Higher wavelength side X-rays are soft X-ray and the lower wavelength side X-rays are hard X-ray. Properties of X-rays Since the X-rays do not deflect by electric and magnetic fields, hence they does not consist of charged particles. X-rays are electromagnetic radiation of very short wavelength. X-rays affect photographic plate like light, but their effect is much more intense than light. X-rays travel in straight lines with the velocity of light. They produce fluorescence in several materials. X-rays ionize the gas through which they pass. X-rays have high penetrating power and can pass through many solids. They produce photo electric effect also. X-rays also show in...

Characteristic X-ray spectrum Line spectrum The methods of producing characteristic X-rays are: In this method we use element as a target in the X-ray tube and electrons are bombarded directly on it. For each target there is a minimum potential below which the line spectra do not appear, and this critical potential difference is different for different element. In this method the primary X-rays from a hard X-ray tube allow to fall on the element. The primary X-rays must be harder than the characteristic X-rays to be produced. The peak obtained in the X-ray spectrum gives the line spectrum, which is the characteristic of the element. Moseley used the potassium ferocynaide as a crystal and photographic plate as a recording medium in place of ionisation chamber in the X-ray spectrometer. He obtained line spectrum by using 30 different targets in tubes and concludes the following: The spectrum obtained by graph has two different groups. Th...