Electronic configuration

• The number of electrons in the outer shell determines whether an atom is reactive or not.
• Each electron shell has a maximum capacity of two electrons per orbital.
• Aufbau Principle: The electrons in an atom are arranged in a fixed order.
• Electrons of Energy levels or shells have a Quantum number, n.
• n 1 has max 2 numbers of electrons
• n 2 has a maximum of 8 electrons
• n 3 has a maximum of 18 electrons
• n 4 has a maximum of 32 electrons
• Sub-shells are the regions of space in which electrons can be found.
• Each subshell is made up of 1 type of atomic orbital, there are s, p, d, f sub-shells.
• Energy level 1: 1s; 2 electrons
• Energy level 2 : 2s 2p ; 8 electrons
• Energy level 3: 3s 3p 3d; 10 electrons
• Energy level 4: 4s 4p 4d 4f; 14 electrons
• An electron shell is made up of atomic orbital with the same principal quantum number, n.
• Sub-shell "s" as max 2 electrons
• Sub-shell "p" as max 6 electrons
• Sub-shell "d" as max 10 electrons
• Sub-shell "f" as max 14 electrons
• Shape of s-orbitals: Spherical, Occurs in every principle energy
• Shape of p-orbital: Dumbell shape, occurs in third principle energy level only
• Shape of d-orbital: Various shape, occurs in fourth principle energy level only
• An Orbital is a region around the nucleus of an atom that can hold up maximum 2 electrons
• Pauli Exclusion principle explains that each orbital can hold up to two electrons with opposite spins.
• Hund's rule state that of maximum multiplicity states that, as far as is possible, electrons will occupy orbitals so that they have parallel spins. This means if a set of sub-shell orbitals of the same energy, eg 2p, 2d,3p,3d; each orbital will singly occupied before pairing