Which element was discovered by Henry Moseley through his X-ray spectra experiments?
A. Electron
B. New way to determine atomic number
C. Neutron
D. Proton
Answer: Option B
Solution (By JKExamLibrary)
Henry Moseley (1913) established the concept of atomic number as the number of protons through X-ray spectra of elements. He showed that atomic number, not atomic mass, is the fundamental property for arranging elements in the periodic table, resolving anomalies in Mendeleev's table. He did not discover a particle but a principle. Modern periodic law is based on atomic number.
Explanation:
Zn + H₂SO₄ → ZnSO₄ + H₂↑. Hydrogen gas is released, which burns with a pop sound. This is a test for hydrogen. Metals above hydrogen in reactivity series displace it from acids. Dilute H₂SO₄ with Zn produces H₂; with Cu, no reaction.
Explanation:
Sodium (alkali metal) reacts violently with cold water: 2Na + 2H₂O → 2NaOH + H₂ + heat. Copper and iron do not react with cold water; iron reacts with steam. Zinc also reacts with steam. Reactivity with water increases down Group 1.
Explanation:
White phosphorus exists as P₄ tetrahedral molecules, containing 4 phosphorus atoms. So atomicity is 4. Sulfur is S₈, oxygen is O₂, ozone O₃. Atomicity is the number of atoms in a molecule of an element. Phosphorus is a non-metal. Red phosphorus is polymeric but P₄ is the common molecular form.
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