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9701 MCQ Solution 14
Question 14:
[Inorganic > Period 3]:
Which diagram represents the change
in ionic radius of the elements across the third period (Na to Cl)?
Reference: Past Exam Paper – November 2002 Paper 1 Q14
Solution 14:
Answer: C.
Going across the third period the first 3 elements are metals. They will
lose electrons from their valence shell to become ions. In this process they
lose a shell and thus significantly decrease the size of their radius. The rest
are non-metals and gain electrons to form ions.
When they do this the valence
shell becomes full. This is best depicted by the sudden rise in option C’s
graph; the first line representing metal cations and the second line
representing non-metal anions.
Between the metal cations the nucleus of the
ions increase in proton number, thus the effect of nuclear charge on the outer
shell is greater, ultimately causing the radius to decrease. This is reason is
the same for the non-metal anions.
The decrease in radius between cations and
anions is best shown by the negative gradient of the 2 lines in option C’s
graph.
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