O Levels Chemistry (5070)•5070/12/M/J/19
Explanation
Element X (atomic number 12) is magnesium, forming XCl₂ chloride
Steps:
- Atomic number 12 identifies X as magnesium (Mg) in the periodic table.
- Magnesium is in group 2, with 2 valence electrons.
- It loses 2 electrons to form Mg²⁺ ions.
- Chloride ions (Cl⁻) require two per Mg²⁺, yielding MgCl₂ or XCl₂.
Why C is correct:
- Group 2 metals achieve octet by +2 oxidation state, bonding with two Cl⁻ ions per the ionic compound formula rule.
Why the others are wrong:
- A: XCl fits group 1 elements with +1 charge, like NaCl.
- B: XCl₃ fits group 13 elements with +3 charge, like AlCl₃.
- D: XCl₄ fits group 14 elements with +4 oxidation, like SnCl₄.
Final answer: C
Topic: Arrangement of elements
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