Shells and Subshells

Shells  

- 1st shell (K): contains s²  

- 2nd shell (L): contains s² p⁶  

- 3rd shell (M): contains s² p⁶ d¹⁰  

- 4th shell (N): contains s² p⁶ d¹⁰ f¹⁴  

Subshells and Maximum Electrons  

- s‑subshell: holds 2 electrons  

- p‑subshell: holds 6 electrons  

- d‑subshell: holds 10 electrons  

- f‑subshell: holds 14 electrons