Which property decreases down a group in the periodic table?
A. Ionization energy
B. Atomic radius
C. Metallic character
D. Number of shells
Answer: Option A
Solution (By JKSSB Mock Tests)
Ionization energy decreases down a group because atomic size increases, and the outermost electron is farther from the nucleus with increased shielding, making it easier to remove. Atomic radius increases, metallic character increases, and number of shells increases down a group.
Explanation:
Dmitri Mendeleev proposed the periodic law based on atomic mass. However, anomalies arose. In 1913, Henry Moseley discovered that the atomic number (number of protons) is the fundamental property. He proposed the modern periodic law: the properties of elements are periodic functions of their atomic numbers.
Explanation:
Ammonium ion (NH₄⁺) contains a coordinate bond: NH₃ donates its lone pair of electrons to H⁺ to form a covalent bond where both electrons come from nitrogen. NaCl is ionic, NH₃ has ordinary covalent bonds, Cl₂ has a nonpolar covalent bond. In NH₄⁺, all four N–H bonds are equivalent after formation. Coordinate bond is also called dative bond and is common in complex ions like [Cu(NH₃)₄]²⁺.
Explanation:
The thermite reaction involves aluminum powder reacting with iron(III) oxide to produce molten iron and aluminum oxide (2Al + Fe₂O₃ → Al₂O₃ + 2Fe). It is highly exothermic and is used for welding railway tracks and repairing metal structures in the field.
No comments yet. Be the first to start the discussion!