The following sketch show the variation in a physical property of third period elements against their number:
What physical property is plotted in this sketch?
A
Ionic radius
B
Melting point
C
Ionization energy
D
Atomic radius
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Propolis Cognitive Error Autopsy
Official Correct Choice:
Option B: Melting point
Concept:
By identifying the shape of a period-trend graph, we can deduce the physical property. A curve that rises to a sharp peak at Group IVA and then drops precipitously is the hallmark of melting/boiling points.
Solution:
The provided sketch (x-axis: atomic numbers 11 through 18) shows a continuous rise peaking at atomic number 14 (Silicon), followed by a sharp fall.
Silicon forms a giant covalent structure, giving it an anomalously high melting point compared to its neighbors.
Therefore, the property plotted is Melting point.
Why other options are incorrect:
Atomic/Ionic radius: These properties generally show a continuous downward trend across a period, not a peak.
Ionization energy: Generally increases across a period, with minor dips (e.g., between Groups IIA/IIIA and VA/VIA), but does not peak exclusively at Group IVA.
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