2019 A Level H2 Chemistry Paper 1 Question 26 - Deduce Electronic Configuration of Mo(IV) Ion

Here's 2019 A Level H2 Chemistry Paper 1 Question 26 on transition elements.

2019 p1 q26 qn

We need to deduce the electronic configuration of molybdenum (IV) ion, given its electronic configuration is similar to those of first row of transition elements and ions.

So the first thing to do is to look up the Periodic Table and find the first row transition element that is directly above molybdenum, which is chromium.

2019 p1 q26 mo and cr

We can figure out the electronic configuration of Cr4+ which is [Ar] 3d2 4s0.

2019 p1 q26 electronic config cr

Students might also be interested in knowing how to write out electronic configuration for the first 30 elements.

Therefore the electronic configuration for Mo4+ will be the same as Cr4+ but the principal quantum number increases by 1 since it is in the next Period, ie [Kr] 4d2 5s0.

2019 p1 q26 electronic config mo

Hence the answer to this question will be option B.

Topic: Transition Elements, Inorganic Chemistry, A Level Chemistry, Singapore

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