EasyChemistryHigh School (9–10)GeneralStructure of the Atom › Electronic Configuration and ValencyNumerical

Use the formula 2n² to find the most electrons that the K, L, M and N shells can hold.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Use the formula $2n^2$ to find the most electrons that the K, L, M and N shells can hold.
What is the total for all four shells?
The M shell can hold more than $8$ . So why does potassium put its $19$ th electron in the N shell?

Need a reminder? The key ideaShow

Shell $n$ holds at most $2n^2$ electrons, and the outermost shell holds at most $8$ . Fill the shells from the inside: for the first twenty elements, $2$ in K, up to $8$ in L, up to $8$ 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.

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← Use the energy levels of hydrogen: K -13.6 eV, L -3.4 eV, M -1.51 eV, N -0.85 eV.Write the electron arrangement of boron (Z = 5), phosphorus (Z = 15) and calcium (Z = 20). →

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