Electron Configuration

Shells & Subshells

Electrons exist in distinct shells within an atom and they can interact with light
Light can behave as a wave or as a particle
Since light can behave as a wave, it has frequency (v) and wavelength (λ)
Frequency and wavelength are related by $c = λ v$ where:
- v is frequency
- λ is wavelength
- c is the speed of light which is approximately 3 x 10⁸ms^-1
Particles of light are called photons
When a photon is absorbed, electrons jump from an inner shell to an outer shell
When a photon is emitted, electrons jump from an outer shell to an inner shell
The energy of the photon (E) is proportional to its frequency (v)
- E α v
The equation used to calculate the energy is E = hv where:
- E is the energy of the photon
- h is the Planck’s constant which is approximately 6.626 x 10^-34J s
- v is the frequency of the photon

Calculate the wavelength of a photon when the energy emitted after an electron transition was 4.81 x 10^-19J

Answer

E = 4.81 x 10^-19J

h = 6.626 x 10^-34J s

c = 3 x 10⁸ms^-1

E = hv

c = λv

E = hv

$v = \frac{E}{h}$

$v = \frac{E}{h}$

$v = \frac{4.81 \times 10^{- 19} J}{6.626 \times 10^{- 34} J s} v = 7.259 \times 10^{14} s^{- 1}$

c = λv

$λ = \frac{c}{v}$

$λ = \frac{c}{v}$

$λ = \frac{3 \times 10^{8} m s^{- 1}}{7.259 \times 10^{14} s^{- 1}} λ = 4.13 \times 10^{- 7} m$

Electrons are organized into shells
- The farther the shell from the nucleus, the higher the energy of those electrons
Each shell contains one or more subshells which are designated as s, p, d, and f
Subshells are further divided into orbitals
Orbitals are regions within a subshell where there is a high probability to find electrons
- The s subshell contains one spherical orbital (spherical shape)
- The p subshell contains three dumbbell-shaped orbitals (p_x, p_y, and p_z)
- The d subshell contains five orbitals, and the f subshell contains seven orbitals
Orbitals can hold a maximum of two electrons

s-orbital-and-p-orbital-shapes

The s orbital is spherical and the p orbital is a dumbbell shape

The max number of electrons depends on the amount of subshells and orbitals that are held in the shell

Summary of the electronic distribution of an atom

Electron configuration is a shorthand notation that describes the distribution of electrons in an atom
It uses the shell and subshell labels to represent the location of electrons
Electrons in the outer shell are called valence electrons
- The number of principal group in the periodic table is equal to number of valence electrons
Electrons in the inner shell are called core electrons