Electron structure

• Electron Shells


  Energy levels where electrons reside around nucleus.
• Quantum Number (n): Indicates main shell number and energy level.
• Orbital: A space around the nucleus that can hold up to 2 electrons of opposite spin. They create the shells. There are different types of orbital, s,p,d,f, all with different shapes.
• s-Orbital: Spherical shape orbital also known as an electron cloud, holds up to 2 electrons. From energy shell 1 upwards each level contains 1 s-orbital within an s sub-shell.
• p-Orbital: An electron cloud that has a 3D dumbbell-shaped orbital. From energy level 2 upwards, each level contains 3 p-orbitals, Px, Py, Pz within a p sub-shell. Each orbital holds 2 electrons so it holds up to 6 electrons in a full p sub-shell.
• d-Orbital: From energy level 3 upwards. Complex shape orbital. There are 5 d orbitals within a d sub-shell therefore holds up to 10 electrons in a full d sub-shell as one orbital holds up to 2 electrons.
• Shell Number (n): Determines distance from nucleus and energy level.
• Maximum Electrons Formula


  Calculated using 2n² for each shell.
• First Shell: Contains 1s orbital, holds 2 electrons, closest to the nucleus, has the lowest energy.
• Second Shell: Contains 2s and 2p orbitals, holds 8 electrons.
• Third Shell: Contains 3s, 3p, and 3d orbitals, holds 18 electrons, with an extra 10 from the transition metals.
• Fourth Shell: Contains 4s, 4p, 4d, and 4f orbitals, holds 32 electrons.
• Sub-shell: Within a shell, orbitals of the same type are grouped together as sub-shells. Each new shell gains a new type of orbital. The number of orbitals increases with each new type. The electrons fit into each orbital so the number of electrons in each sub-shell also increases.
• What is electron spin? A property of electrons represented as up or down arrows.
• What does electron spin represent in paired electrons? The repulsion between two paired electrons within the same orbitals, raising their energy.
• How do single electrons in the same orbitals within the same sub-shell spin? They will spin in the same direction, and remain unpaired until they're forced to pair.
• When do electrons pair in orbitals? Electrons only pair when forced to because there are no empty orbitals available within the sub-shell.
• Paired Electrons: Electrons in the same orbital with opposite spins.
• Orbital Box Diagram: Visual representation of electron distribution in orbitals.
• Electron Cloud: Model representing probable locations of electrons. Electron shells make up a model that helps to visualize something that can't be seen forms a cloud.
• Energy Levels: Quantized states of energy for electrons in atoms. Made up of atomic orbitals.
• Transition Metals


  Elements with partially filled d-orbitals.
• Orbital Capacity: Each orbital can hold a maximum of 2 electrons.
• Electron Configuration


  Arrangement of electrons in atomic orbitals.
• Electron configuration symbol (nm^x): n= number of main energy shell

  m= number of energy sub-shell

  x= number of electrons in the same energy sub-shell
• 3D Orbital Representation


  Visualizes p orbitals as three-dimensional shapes.
• Energy Level: Main shell where electrons are, denoted by n.
• 3d8


  Indicates 8 electrons in the third d sub-shell.
• 2p6


  Indicates 6 electrons in the second p sub-shell.
• What is the first rule of filling electrons in orbitals? Electrons are added one at a time.
• Which energy levels fill first when adding electrons? The lowest available energy level fills first.
• What is the rule regarding filling main shells? Each main shell should be full before moving onto the next.
• Do transition metals always follow the main shell filling rule? Some transition metals don't always follow this rule.
• In p and d orbitals, how do electrons fill the orbitals? Each orbital fills singly before pairing occurs.
• Why do electrons in the same orbital remain unpaired initially? Repulsion between electrons in the same orbital and the same sub-shell.
• What is the spin orientation of electrons in the same orbital before pairing? Electrons have spin in the same direction until they're forced to pair.
• What is the relationship between the spins of electrons in each orbital? Electrons in each orbital have opposite spin.
• What type of energy states are favored in electron configuration? Low energy states are favored (they're stable)
• Which sub-shell has a lower energy: s, p, or d? s has a lower energy than p, and p has a lower energy than d.
• How does the energy of a shell relate to its distance from the nucleus? The nearer the shell is to the nucleus, the lower its energy.