An element 'X' has electronic configuration 2,8,7. It belongs to:
A. Group 7, Period 2
B. Group 18, Period 3
C. Group 17, Period 3
D. Group 16, Period 3
Answer: Option C
Solution (By JKExamLibrary)
Atomic number = 2+8+7=17 (chlorine). Period = number of shells = 3. Valence electrons = 7 → Group 17 (10+7 for p-block). Group 18 has 8 valence electrons.
Explanation:
Hydrochloric acid (HCl) is commonly used for pickling (cleaning) steel to remove rust and scale (iron oxides) before further processing like galvanizing or plating. Reaction: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O. Sulfuric acid is also used. Nitric acid is an oxidizer and would passivate some metals. Acetic acid is too weak.
Explanation:
Elements in the same vertical column (group) have the same number of electrons in their outermost shell (valence electrons). This gives them similar chemical properties. The number of shells increases as we go down a group, leading to trends in atomic radius and ionization energy.
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