Electron Shells, Sub-Shells & Orbitals

• What are electron shells?

  Electron shells are energy levels around the nucleus where electrons are found. They are labeled as etc.
• How many electrons can each shell hold?

  First shell (): 2 electrons Second shell (): 8 electrons Third shell (): 18 electrons Fourth shell (): 32 electrons
• How many electrons can each shell hold?

  First shell (): 2 electrons Second shell (): 8 electrons Third shell (): 18 electrons Fourth shell (): 32 electrons
• What are sub-shells?


  Sub-shells are divisions within an electron shell, labeled as s, p, d, and f, which determine the shape of the electron cloud.
• How many orbitals are there in each sub-shell?

  s sub-shell: 1 orbital (holds 2 electrons). p sub-shell: 3 orbitals (holds 6 electrons). d sub-shell: 5 orbitals (holds 10 electrons). f sub-shell: 7 orbitals (holds 14 electrons).
• What is the order of filling sub-shells with electrons?

  Electrons fill sub-shells in the order of increasing energy: etc.
• What is the order of filling sub-shells with electrons?

  Electrons fill sub-shells in the order of increasing energy: etc.
• Why does fill before ?

  The sub-shell is lower in energy than , so it fills first.
• What is an orbital?

  An orbital is a region within a sub-shell where there is a high probability of finding an electron.
• How many electrons can each orbital hold?

  Each orbital can hold a maximum of 2 electrons with opposite spins.
• What are the shapes of s and p orbitals?

  s orbitals are spherical.

  p orbitals are dumbbell-shaped.