MediumChemistryHigh School (9–10)GeneralStructure of the Atom › Electronic Configuration and ValencyConceptualBoard Exam
A student writes the electron arrangement of sodium, which has 11 electrons, as 2, 9…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- A student writes the electron arrangement of sodium, which has electrons, as . What is the mistake? What is the correct arrangement?
- Another student writes calcium, with electrons, as . What is wrong this time?
Need a reminder? The key ideaShow
Shell holds at most electrons, and the outermost shell holds at most . Fill the shells from the inside: for the first twenty elements, in K, up to in L, up to in M, and the rest in N.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The L shell can hold at most , not . After and , the left goes into the M shell: .
Step 2. (b) Here the M shell would be the outermost shell, with electrons. An outermost shell holds at most . So M takes and the last start the N shell: .
Answer: (a) . (b) .
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