Ch 5-2 Quantum Mechanical Model

5-2 QUANTUM THEORY OF THE ATOM 

Bohr Model of the Atom  

Used to explain why AES was set of discontinuous lines of specific frequencies (color). Proposed that Hydrogen atoms have only certain allowable energy states based on Planck’s and Einstein’s quantized energy.  

 

Ground state- lowest allowable energy states of an atom. Excited state- atom gains energy; H atoms can have many different excited states although it contains 1 e-.

Electrons move around a H atom in circular orbit Orbits equal to a principal quantum number n, where n=1 is lowest nrg level, closest to nucleus.

BOHR MODEL OF THE ATOM 

n =6 n =5 n =4 n =3 n =2 n =1

nucleus

Orbits/ levels are like rungs in step ladder  

Cannot stand b/w rungs, ecan’t exist b/w levels (orbits). E- move from 1 orbit to the next emitting or absorbing certain amts of nrg (quanta). 



The smaller the e- orbit, the lower the energy state/level The larger the e- orbit, the higher the energy state/level

BOHR MODEL OF THE ATOM 

Hydrogen’s Line Spectrum (AES) At n= 1 H atom is in ground state  When nrg is added, e- moves to higher energy level, n=2 (excited state).  E- drop back to lower energy level n=1 and emitts a photon equal to the difference b/w levels. 

A photon is emitted with E= hυ

A photon is absorbed

HYDROGEN’S LINE SPECTRUM

Energy of Hydrogen Atom



Lines which show up have specific energies which correspond to a frequency of a color of light.

E= 4.85 x 10-19 J

n 6 5 4 3

E= 3.03 x 10-19 J 2

1

A photon is emitted with E= hυ for each frequency

5-2 QUANTUM THEORY AND THE ATOM 

Quantum mechanical model is the modern atomic model and comes from Louis De Broglie: radiation (energy) behaves like particles and vice versa.

A. 1. 2.

All particles w/ a mass have wave characteristics E- move around nucleus in a wave-like manner

Heisenberg uncertainty principle- impossible to know both the velocity and position of an e- at the same time. Shrodinger: e-’s energy are limited to certain Photon values (quantum) Photon but does not predict path

B.

C.

wavelength

Treated e-’s as waves changes 2. Created wave function = predicts probability of finding Before After e- in a volume of space (location) 1.

Moving Electron

Electron velocity changes

HYDROGEN’S ATOMIC ORBITALS Shrodinger’s wave eqn predicts atomic orbitals  Atomic orbital - 3D regions around the nucleus that describes the e-’s probable location. 

atomic orbital = fuzzy cloud b. Do not have a defined size c. Shape = volume that contains 90% of the probable location of e-’s inside that region. a.

QUANTUM MECHANICAL MODEL 

Like Bohr, electrons occupy space surrounding nucleus and exist in several principal energy levels = principal quantum number (n) Relative size and energies of atomic orbital  n = 1,2, 3, etc. = period 



Principal nrg levels consist of energy sublevels with different nrg values. 

Energy sublevels – shape of the atoms’ orbitals s = spherical p = dumbbell d, f= different shapes

QUANTUM MECHANICAL MODEL 

Principal energy levels have specific allowed sublevels - shapes.

s

p s

d p

s

p s



f

4

d

3 2 n= 1

s sublevel is lower in energy and f has higher energy

QUANTUM MECHANICAL MODEL 

Sublevels consist of orbitals of different orientation. Orbitals in same sublevel are = in energy (no matter orientation)  Orbitals only hold 2e- maximum with opposite spins (+ or – spins). Sublevel Orientations/ Orbitals Max # es 1 2 p 3 6 d 5 10 f 7 14 