Chapter – 1 Atomic Spectroscopy

(주기율표) Group 3 4 5

Pauli Exclusion Principle (Pauli 배제 원칙) The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins. Two electrons in a single orbital must have different values of ms This statement demands that if there are two electrons in an orbital one must have ms = +1/2 (spin up ) and the other must have ms = -1/2 (spin down ) An electron in an orbital is fully described by the four quantum numbers: n, l, ml and ms

Quantum numbers (양자 수) are summarized as follows: Name Symbol Orbital meaning Range of values Value examples principal quantum number n shell 1 ≤ n n = 1, 2, 3, … azimuthal quantum number (angular momentum) ℓ subshell (s orbital is listed as 0, p orbital as 1 etc.) 0 ≤ ℓ ≤ n − 1 for n = 3: ℓ = 0, 1, 2 (s, p, d) magnetic quantum number, (projection of angular momentum) mℓ energy shift (orientation of the subshell's shape) −ℓ ≤ mℓ ≤ ℓ for ℓ = 2: mℓ = −2, −1, 0, 1, 2 spin projection quantum number ms spin of the electron (−½ = "spin down", ½ = "spin up") −s ≤ ms ≤ s for an electron s = ½, so ms = −½, ½

Electronic configuration of Europium Atomic Number - - 63 Electronic configuration - [Xe] 4f75d06s2 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d0 4f7 Orbit (n) orbital (s, p d f) Total Number of electrons 1 1s2 2 2 2s22p6 8 3 3s23p63d10 18 4 4s24p64d104f7 25 5 5s25p65d0 8 6 6s2 2 Total – 63 electrons oxidation states (valence) - +2, +3  

• Selection Rules for electric dipole transitions: ∆L = ±1, ∆S = 0, ∆J = 0, ±1 but not J = 0 to 0. Fine Structure: Atom in Magnetic Field • Selection Rule for weak field: ∆MJ = 0, ±1 but not from 0 to 0