The Quantum Mechanical Model of the atom and Quantum Numbers 3.3 and 3.4

Quantum Mechanics Each electron is a wave that can be described by a series of “quantum numbers” There are four quantum numbers: n, l, ml, ms The combination of the first defines an “orbital”

The Quantum Numbers The principal quantum number is n n ranges from 1 to infinity Bohr said n represented shell number or energy level. n=1 is smallest (closest to nucleus) n defines size and energy

The secondary quantum number is l- angular quantum number l ranges from 0 to n - 1, in increments of one l represents the subshell Q - what are the possible values of l when n=3 A - start at 0 go to n - 1  0, 1, 2 Q - what are the possible values of l when n=6 A - 0, 1, 2, 3, 4, 5

The secondary Quantum Number Whereas n represents size and energy, l tells us of the shape of an electron area. 0 = s, 1 = p, 2 = d, 3 = f s is “spherical”, p is figure eight “dumbbell”, d is “fat x”, f is “jacks and flowers” We often identify electrons by shell and subshell: e.g. 1s, 3d, 2s, and 5d subshell

l : The secondary quantum number If n can be thought of as shells, l can be thought of as “subshells” dividing each shell into subsections … (l = 0  n - 1) n = 1 l = 0 (s) n = 3 l = 0 (s) l = 1 (p) l = 2 (d) n = 2 l = 0 (s) l = 1 (p) For more lessons, visit www.chalkbored.com

s p d orbitals

F Orbitals

Magnetic Quantum Number ml, The magnetic quantum number ml is the orientation of the orbital s only one orientation ml= 0 p three orientations x,y,z ml= -1, 0, 1 d five orientations ml= -2,-1, 0, 1, 2

Spin quantum number ms, ms= -1/2 or +1/2 Counter clockwise or clockwise Two electrons fit in each orbital and must have must have an opposite spin Denoted by up and down arrows

Rules for Filling Orbitals Aufbau principle: Electrons always fill orbitals of lower energy first. 1s is filled before 2s, and 2s before 2p. The Pauli Exclusion Principle states no two electrons within a particular atom can have all four identical quantum numbers. In function, this principle means that if two electrons occupy the same orbital, they must have opposite spin. Hund's Rule states that when an electron joins an atom and has to choose between two or more orbitals of the same energy, the electron will prefer to enter an empty orbital rather than one already occupied. That means put 1 electron in px, one in py then one in pz before putting a second in px.

Orbitals 2 electrons fit in each orbital Lowest energy orbitals fill first orbital energy diagram

Shish kebob method

Periodic table method

Writing Energy Level Diagrams Use The aufbau principal, Hunds Rule and The Pauli expulsion Principal to write in the electrons for the element : Sulphur

Writing Energy Level Diagrams Use The aufbau principal, Hunds Rule and The Pauli expulsion Principal to write in the electrons for the element : Iron

Linking to previous knowledge Think back to grade nine…..how many electrons in the first level?? 2 (1s2) How many in the second?? Third?? 8 (1s2 2s22p6) 18 (1s2 2s22p6 3s23p6 4s2 3d10) Why did we never talk past element #20?? Can you block out the periodic table with the orbital subshells in mind?? S shell column 1,2…

Electron Configuration

Using the periodic table, write the complete electronic configuration for each: Cl Sr I

Using the periodic table, write the complete electronic configuration for each: Cl 1s2 2s2 2p6 3s2 3p5 Sr 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 I 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5

Expanded versus condensed electron configuration Condensed version- start with the noble gas that precedes the element Cl Sr I

Electron configuration explains many things Why do transition elements have multivalence? Fe Fe +2 Fe +3 Sn Sn +2 Sn +4 Why are some elements magnetic? Ferromagnetic materials are strongly attracted by a magnetic force. The elements iron (Fe), nickel (Ni), cobalt (Co) and gadolinium (Gd) are such materials. Paramagnetic- can be made to be attracted like manganese (Mn), Ruthenium, (Ru) Rhodium, (Rh), Platinum (Pt), Europium (Eu)…

Exceptions to electron configurations Chromium and all those below it Copper and all those below it