Quantum Mechanical Model of the Atom

Progression of Atomic Theory

Bohr Model Energy levels 1st energy level can hold 2 2nd energy level can hold 8 3rd energy level can hold 8 Bohr Model Breaks down after 3rd energy level and no longer applies to Modern Quantum Mechanical Model of the Atom

Bohr Model for Hydrogen Energy level of an electron analogous to the rungs of a ladder The electron cannot exist between energy levels, just like you can’t stand between rungs on a ladder A quantum of energy is the amount of energy required to move an electron from one energy level to another The Bohr model explained the emission spectrum of the hydrogen atom but did not always explain those of other elements.

The Quantum Mechanical Model In 1926, Erwin Schrodinger derived an equation with 4quantum numbers that described the energy and position of the electrons in an atom The 4 quantum numbers are used in the electron configuration which is a notation using energy levels and sublevels to show how the electrons are distributed within the atom.

Quantum Numbers Chem Saver p 23 Row # = Energy level or distance from nucleus Possibilities 1 –7 7 Rows Subshell Possibilities are s, p, d, or f 4 subshells 1 S # electrons occupying this orbital Possibilities are: s: 1 or 2 p: 1-6 d: 1-10 f: 1-14

Energy Levels and Sublevels The first energy level has only one type of orbital (sublevel) S The second energy level has 2 types of orbitals S and P The third energy level has three types of orbitals S, P and D The fourth energy level has four types of orbitals S, P, D and F Successive energy levels follow the same pattern. Relative energy: s < p < d < f

(sublevels available) Principal Energy Level (n=?) Orbital Types (sublevels available) 1 s 2 p 3 4

Orbital Shapes s orbital: (one possible orientation)

Orbital shapes P orbital: ( three possible orientations)

Orbital shapes d: orbital: ( five possible orientations)

Orbital shapes f orbital: (seven possible orientations)

The Quantum Atom

(sublevels available) Orbital Types (sublevels available) # of orbital's per level s 1 p 3 d 5 f 7

Total # of orbitals per P.E.L. (n2) Principal Energy Level (n=?) Total # of orbitals per P.E.L. (n2) 1 2 3 4

(sublevels available) # of e’s per orbital type s 2 p 6 d 10 f 14

Total # of e’s per P.E.L. (2n2) Principal Energy Level (n=?) Total # of e’s per P.E.L. (2n2) 1 2 3 4

Electron Configurations Electrons fill the lowest energy levels first (H, Z=1) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s1

Lewis Dot Structures Lewis dot structures are shorthand to represent the valence electrons of an atom. The structures are written as the element symbol surrounded by dots that represent the valence electrons.

Lewis Dot Structures E N E R G Y Review Electron Configuration (H, Z=1) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s1

Pauli Exclusion Principle Fourth Quantum number is the Spin Pauli Exclusion Principle no two e- in an atom can have the same four quantum numbers. each electron needs its own space. Result – an orbital can hold a maximum of 2 electrons with opposite spin

Electron Configurations Electrons fill the lowest energy levels first (He, Z=2) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s2

Electron Configurations Electrons fill the lowest energy levels first (Li, Z=3) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s1

Electron Configurations Electrons fill the lowest energy levels first (Be, Z=4) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s2

Electron Configurations Electrons fill the lowest energy levels first (B, Z=5) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p1

Hund’s Rule Don’t pair electrons in degenerate orbitals until necessary. Unpaired electrons have the same spin. Applies to p, d, and f orbitals 2p 3d

Electron Configurations Electrons fill the lowest energy levels first (C, Z=6) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p2

Electron Configurations Electrons fill the lowest energy levels first (N, Z=7) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p3

Electron Configurations Electrons fill the lowest energy levels first (O, Z=8) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p4

Electron Configurations Electrons fill the lowest energy levels first (F, Z=9) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p5

Electron Configurations Electrons fill the lowest energy levels first (Ne, Z=10) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p6

Electron Configurations Electrons fill the lowest energy levels first (Na, Z=11) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p63s1

Lewis Dot Structures Chem Saver p 24 Lewis dot structures are shorthand to represent the valence electrons of an atom. The structures are written as the element symbol surrounded by dots that represent the valence electrons.

Electron Configurations Your Turn: Try Krypton (Kr, Z=36) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s

Electron Configurations Electrons fill the lowest energy levels first (Ca, Z=20) 4d E N E R G Y 5s 4p 3d 4s 3p 3s 2p 2s 1s 1s22s22p63s23p64s2

An internet program about electron configurations is: (Just click on the above link)

Diagonal Rule for Writing Configurations and Practice Chem Saver p 23

The relation between orbital filling and the periodic table Chem Saver p 23 ns1 np1 n-1d1 n-2f1

In your composition notebook complete, Z=11 to 54 odd only In your composition notebook complete, Z=11 to 54 odd only. Be sure to show the electron configuration short hand notation and the Lewis dot structure for each.

Electron Configuration on the Periodic Table The elements in the same family groups on the periodic table have similar physical and chemical properties The elements in the same family groups also tend to form similar types of compounds with other elements This is because the elements in the same family groups have the same number of electrons in the outer energy level

Short Hand noble gas configurations