Quantum Theory
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What did Niels Bohr predict?
electrons exist in orbits with specific energy
What does atomic emission spectra provide evidence f?
subshells within each energy level
What does classical theory assume electrons exist as?
a particle (with mass and charge)
What does experimental evidence show that electrons can have?
wave-like properties (show diffraction and interference)
What does the wave-like nature of electrons make it impossible to do? What is this known as?
specify exactly the position and momentum of the electron - Heisenburg Uncertainty Principle
How can the discrete lines seen in the emission spectra be explained?
if the electron is regarded as having the properties of both particles and waves
What does quantum theory suggest? (3)
Electrons within atoms behave as waves of different shapes and sizes The waves are known as orbitals Each orbital can hold a maximum of two electrons
What are orbitals defined by?
Quantum numbers
What is an orbital?
a region of space where the probability of finding the electron is >95% (i.e. there is uncertainty)
What are the shapes of orbitals?
S P D
What are S orbitals said to be?
spherically symmetrical
How many types of S orbitals are there?
1
What is the maximum number of electrons S orbitals hold?
2
What is the maximum number of electrons P orbitals hold?
6
What are the 3 types of P orbitals?
Px Py Pz
What are the 3 P orbitals described to be?
degenerate, i.e. have the same energy
What is the maximum number of electrons D orbitals hold?
10
What are the 5 types of D orbitals?
dxy dxz dyz dx2-y2 dz2
What are the 5 D orbitals described to be?
degenerate, i.e. have the same energy
Describe the principal quantum number
n Tells us the main energy level n has values from 1 to infinity first shell n=1
Describe the angular momentum quantum number
This describes the shape of the orbital and tells us which subshells are present in the principal shell l=0 - S l=1 - p l=2 - d
Describe the magnetic quantum number
Gives u the number of each type of orbital m has values from -l to +l l= 0 = one S orbital l=1 = -1,0,1 = 3 p orbitals
What do electrons appear to do?
spin on their axis
What do spinning charges create?
a magnetic field