Chemistry S & P Block Elements MDCAT 2011
PMDC Verified Question 101 of 104
The diagram below is a plot of melting points of elements of second period against their atomic numbers. Lithium and fluorine are placed at the extreme ends of the plot. On the basis of melting points where would you place carbon among the empty slots on the plot?

3 Li 1 2 3 4 O F Ne
A
1
B
4
C
2
D
3
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 3
Concept:

Along a short period (like the second period), the melting point of elements increases up to Group IVA (Group 14) and then steeply decreases.

Solution:

  • Carbon is in Group IVA. Elements in this group form giant covalent network structures (like diamond), which require a massive amount of energy to break.
  • Therefore, Carbon has the highest melting point in the second period.
  • Looking at the plot, position 3 represents the highest peak on the graph, which corresponds to Carbon.


Why other options are incorrect:

  • Options 1, 2, and 4 represent elements with lower melting points (such as Beryllium, Boron, or Nitrogen/Oxygen) which do not form giant covalent lattices as strong as Carbon.

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