Question

Element X forms a chloride with the formula XCl₂, which is solid with a high melting point. X would most likely be in the same group of the Periodic Table as

• A. Sodium (Na)
• B. Magnesium (Mg)
• C. Aluminum (Si)
• D. Silicon (Si)

Answer 1

The correct option is B

Magnesium (Mg)

The explanation for the correct option

(B): Valency: is the combining power of an element. Elements in the same group of the periodic table have the same valency.

• The valency of an element is related to how many electrons are in the outer shell.
• Element X forms a chloride with the formula XCl₂ which means X needs to donate 2 electrons to the chlorine atoms.
• Mg has 2 valency electrons so it forms ${\mathrm{MgCl}}_2$.

The explanation for the incorrect answer

option (A): Na has 1 valency, so it forms $\mathrm{NaCl}$.

option (C): Al has 3 valencies, as a result, it forms ${\mathrm{AlCl}}_3$.

option (D): Si has 4 valencies, so it forms ${\mathrm{SiCl}}_4$.

Thus the correct option is option (B): Element X forms a chloride with the formula XCl₂, which is solid with a high melting point. X would most likely be in the same group of the Periodic Table as Magnesium.