Chemistry · Ionic bonding
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Magnesium sulfide is made when magnesium reacts with sulfur. Magnesium is in Group 2 and sulfur is in Group 6 of the periodic table. Explain how magnesium sulfide forms and why solid magnesium sulfide does not conduct electricity but molten magnesium sulfide does.
Level 3 (5-6): Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account. Level 2 (3-4): Relevant points (reasons/causes) are identified, and there are attempts at logically linking. The resulting account is not fully clear. Level 1 (1-2): Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking. No relevant content (0).
Magnesium reacts with sulfur and makes a solid called magnesium sulfide. The atoms stick together. It does not conduct electricity as a solid because it is not able to let electricity through, but when it is melted it may conduct because it is hot and the particles can move.
What this answer missed
- •Each magnesium atom loses two electrons and each sulfur atom gains two electrons
- •The electron transfer forms Mg²⁺ magnesium ions and S²⁻ sulfide ions
- •Solid magnesium sulfide does not conduct because its ions are held in fixed positions and cannot move to carry charge
- •Molten magnesium sulfide conducts because its ions are free to move and carry charge
Magnesium gives electrons to sulfur and ions are made. Magnesium sulfide is solid, so it cannot conduct electricity, but when it is melted the particles can move around and it can conduct.
What this answer missed
- •each magnesium atom loses two electrons and each sulfur atom gains two electrons
- •magnesium forms Mg²⁺ ions and sulfur forms S²⁻ ions, called sulfide ions
- •solid magnesium sulfide does not conduct because its ions are held in fixed positions and cannot move to carry charge
Magnesium is in Group 2, so it loses two electrons and becomes a Mg2+ ion. Sulfur gains electrons and becomes negative, so the two types attract and make magnesium sulfide. In the solid the ions are held in place, so they cannot conduct. When it is molten, the electrons can move around, so it conducts.
What this answer missed
- •Sulfur gains two electrons and forms S2− sulfide ions.
- •When magnesium sulfide is molten, its ions are free to move and carry charge, so it conducts electricity; it is not electrons that move through the molten compound.
Each magnesium atom loses two electrons and becomes a Mg2+ ion. A sulfur atom gains the two electrons and becomes an S2− ion. The oppositely charged ions form an ionic compound and are arranged in a lattice. In solid magnesium sulfide the ions are fixed in position, so they cannot move and carry charge. When it is molten, the ions are free to move, so it conducts electricity.
- •Each magnesium atom loses two electrons to form a Mg2+ ion.
- •Each sulfur atom gains two electrons to form an S2− ion.
- •The oppositely charged ions form an ionic compound arranged in a lattice.
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