Louis De Broglie (1924)
– Proposed that ALL matter has wave and particle properties, not just electrons. – E = E E = hυ or E = hc/λ & E = mc2 – hc/λ = mc2 hc = mc2λ h = mcλ – λ = h/mc OR λ = h/mv – Example:
λ of baseball (mass = .2 kg and v = 30 m/s) λ of an electron (mass = 9.11 x 10-31 kg and v = 3 x 108 m/s)
– Said that because of size and speed it is impossible to know both exact position and momentum of and electron at the same time. – This is referred to as “Heisenberg Uncertainty Principle” – To “see” an electron we strike it with something of similar size and observe its behavior.
We cannot see an electron directly.
– We use photons of energy to do this.
The work of de Broglie, Schroedinger, Born, and Heisenberg led to the study of “quantum mechanics” (motion in increments) 1. classical physics
– describes the motion of bodies much larger than the atoms of which they are composed. – energy can be gained or lost in any amount
2. quantum physics
– describes the motion of atoms and subatomic particles as waves. – particles gain or lose energy in packets called “quanta”
Wave Mechanical Model
– Developed the “wave mechanical model” of the atom – He used the following equation to produce scatterplots that are now called “electron clouds”
E = 22me2/h2n2
– These electron clouds are areas in which there is a great probability of finding an electron (90%). – The cloud is more dense where the probability of finding an electron is high. – The cloud is less dense where the probability of finding an electron is low. – This is called an “orbital” – a region in space in which there is a high probability of finding an electron.
Each component is given a letter & a name – we call them “quantum values” 1. n = principal
– distance from the nucleus
Energy Components in Electrons
2. l = azimuthal
– angular momentum
3. m = magnetic
– interaction with electromagnetic fields
4. s = spin
– axial rotation
Using these we can pinpoint the exact location of an e-.
n = principal energy level (shell) n + l = energy sublevel (subshell); defines the type of orbital that the electron is in n + l + m = specific orbital (axis orientation) n + l + m + s = spin (exact electron), identifies the exact electron and its location ANALOGY
S-orbital = spherical shape, only 1 of them P-orbital = gumdrop or dumbell shape, 3 of them – one on each axis (x,y,z) D-orbital = donut shape, 5 of them F-orbital = cigar shape, 7 of them Each orbital contains a max of 2 electrons Orbit – path of an electron (according to Bohr) Orbital – region in space where there is a high probability of finding an electron
ENERGY LEVELS n=1 n=2 n=3
ORBITAL TYPES s s,p s,p,d
# OF ORBITALS 1 4 9
# OF ELECTRONS 2 8 18
Energy level = the number of orbital types Total number of orbitals in an energy level = n2 Total number of electrons in any energy level = 2n2