Principles and Laws that Principles and Laws that Explain Electron Explain Electron

BehaviorBehavior

SC3: Students will use the modern atomic theory SC3: Students will use the modern atomic theory to explain the characteristics of atoms.to explain the characteristics of atoms.

Heisenberg Uncertainty PrincipleHeisenberg Uncertainty Principle States that it is impossible to determine States that it is impossible to determine

simultaneously both the position and velocity of simultaneously both the position and velocity of an electron or any other particle.an electron or any other particle.

This means that if one knows the position of an This means that if one knows the position of an electron, then one cannot know the velocity it is electron, then one cannot know the velocity it is traveling in the atom.traveling in the atom.

If one knows the electron’s velocity, then one If one knows the electron’s velocity, then one cannot know the position at that moment.cannot know the position at that moment.

Schrodinger Wave EquationSchrodinger Wave Equation This equation was developed by an Austrian This equation was developed by an Austrian

physicist Erwin Schrodinger who believed that physicist Erwin Schrodinger who believed that electrons had a dual wave-particle nature like electrons had a dual wave-particle nature like light. In conjunction with the Heisenberg light. In conjunction with the Heisenberg Uncertainty Principle, his work led to the Uncertainty Principle, his work led to the Quantum Theory. The Quantum Theory Quantum Theory. The Quantum Theory describes mathematically the wave properties of describes mathematically the wave properties of electrons and other very small particles. From electrons and other very small particles. From the Quantum Theory came the concept of the Quantum Theory came the concept of quantum numbers and what those would quantum numbers and what those would represent.represent.

Quantum NumbersQuantum Numbers Quantum numbers specify the Quantum numbers specify the

properties of atomic orbitals and the properties of atomic orbitals and the properties of electrons in orbitals.properties of electrons in orbitals.

There are four quantum numbers: There are four quantum numbers: 1. Principal1. Principal

2. Angular 2. Angular 3. Magnetic 3. Magnetic 4. Spin 4. Spin

Quantum Number ChartQuantum Number ChartQuantum Quantum NumberNumber

SymbolSymbol DefinitionDefinition ExamplesExamples

PrincipalPrincipal nn the main the main energy levelenergy level

Positive integers…1,2, Positive integers…1,2, 3, etc.3, etc.

AngularAngular l l the shape of the shape of the orbitalthe orbital

Positive integers with Positive integers with zero…(n-1) is the zero…(n-1) is the formulaformula

MagneticMagnetic mm Orientation of Orientation of orbital around orbital around the nucleusthe nucleus

Positive and negative Positive and negative and indicate number of and indicate number of orbitals present (m= -1)orbitals present (m= -1)

SpinSpin ss Spin of the Spin of the electronselectrons

Must be opposite…Must be opposite…number form +1/2 and number form +1/2 and -1/2-1/2

Aufbau PrincipleAufbau Principle States that electrons fill an atom based on States that electrons fill an atom based on

energy levels, starting at lowest energy level energy levels, starting at lowest energy level and moving out to higher energy levels.and moving out to higher energy levels.

The further an electron is from the nucleus, The further an electron is from the nucleus, the higher the energy level and energy of the higher the energy level and energy of that electron.that electron.

Electron configuration is a way to represent Electron configuration is a way to represent this principle.this principle.

Pauli’s Exclusion PrinciplePauli’s Exclusion Principle States that electrons may NOT have the same States that electrons may NOT have the same

exact quantum number, which means that if two exact quantum number, which means that if two electrons occupy the same orbital, they MUST electrons occupy the same orbital, they MUST have opposite spins.have opposite spins.

This principle is BEST represented by the This principle is BEST represented by the orbital-filling diagrams. orbital-filling diagrams.

Chemists represent the opposite spins in three Chemists represent the opposite spins in three ways: ways: 1. arrows (one up and one down)1. arrows (one up and one down)

2. +1/2 and -1/22. +1/2 and -1/23. CW and CCW3. CW and CCW

Hund’s RuleHund’s Rule

Due to the negative charge on all electrons, Due to the negative charge on all electrons, electrons prefer to be alone if possible. This electrons prefer to be alone if possible. This means that if additional orbitals are available, means that if additional orbitals are available, then electrons will go to an open orbital before then electrons will go to an open orbital before pairing up with another electron. Pairing starts pairing up with another electron. Pairing starts when all orbitals have their FIRST electron when all orbitals have their FIRST electron present.present.

Represented by orbital-filling diagrams and Represented by orbital-filling diagrams and Lewis dot diagrams.Lewis dot diagrams.

An Example…An Example…Oxygen: 1sOxygen: 1s222s2s222p2p44

Quantum Numbers:Quantum Numbers:n =1 l = 0 m = 0 s = +1/2, -1/2n =1 l = 0 m = 0 s = +1/2, -1/2n = 2 l = 0 m = 0 s = +1/2, -1/2n = 2 l = 0 m = 0 s = +1/2, -1/2n = 2 l = 1 m = -1 s = +1/2, -1/2n = 2 l = 1 m = -1 s = +1/2, -1/2n = 2 l = 1 m = 0 s = +1/2n = 2 l = 1 m = 0 s = +1/2n = 2 l = 1 m = +1 s = +1/2n = 2 l = 1 m = +1 s = +1/2