IB Chemistry SL

Revision Notes

2.1.7 Sublevels & Orbitals

Electron Orbitals

  • Each shell can be divided further into subshells, labelled s, p, d and f
  • Each subshell can hold a specific number of orbitals:
    • s subshell : 1 orbital
    • p subshell : 3 orbitals labelled px, py and pz
    • d subshell : 5 orbitals
    • f subshell : 7 orbitals
  • Each orbital can hold a maximum number of 2 electrons so the maximum number of electrons in each subshell are as follows:
    • s : 1 x 2 = total of 2 electrons
    • p : 3 x 2 = total of 6 electrons
    • d : 5 x 2 = total of 10 electrons
    • f : 7 x 2 = total of 14 electrons
  • In the ground state, orbitals in the same subshell have the same energy and are said to be degenerate, so the energy of a px orbital is the same as a py orbital

Atomic Structure Electrons in Atoms, downloadable AS & A Level Chemistry revision notes

Shells are divided into subshells which are further divided into orbitals

Summary of the arrangement of electrons in atoms table

Atomic Structure Electrons in Atoms Table, downloadable AS & A Level Chemistry revision notes

The s & p Orbitals

s orbitals

  • The s orbitals are spherical in shape
  • The size of the s orbitals increases with increasing shell number
    • E.g. the s orbital of the third quantum shell (n = 3) is bigger than the s orbital of the first quantum shell (n = 1)

Atomic Structure The s Orbitals, downloadable AS & A Level Chemistry revision notes

The s orbitals become larger with increasing principal quantum number

p orbitals

  • The p orbitals are dumbbell-shaped
  • Every shell has three p orbitals except for the first one (n = 1)
  • The p orbitals occupy the x, y and z axes and point at right angles to each other, so are oriented perpendicular to one another
  • The lobes of the p orbitals become larger and longer with increasing shell number

Atomic Structure The p Orbitals, downloadable AS & A Level Chemistry revision notes

The p orbitals become larger and longer with increasing principal quantum number

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