Electrons in the Atom

Heisenberg Uncertainty Principle

• This is the theory that states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.

Quantum Theory• Schrodinger derived an equation that

described energy & position of electrons in atom

• Schrodinger along with other scientists laid the foundation for the modern quantum theory, which describes mathematically the wave properties of electrons and other very small particles.

Orbitals & Quantum Numbers• Electrons exist around the nucleus in

certain regions called atomic orbitals - 3D regions around the nucleus that indicates the probable location of an electron.

• Quantum numbers are used to describe atomic orbitals. The quantum numbers are like an address for the electrons.

S orbitals

• 1 s orbital for every energy level• Spherical

shaped• can hold 2 electrons• Called the 1s, 2s, 3s, etc.. orbitals.

P orbitals• Start at second energy level • 3 different directions• 3 different shapes• Each can hold 2 electrons

P Orbitals

D orbitals• Start at third energy level • 5 different shapes• Each can hold 2 electrons

F orbitals

• Start at fourth energy level• 7 different shapes• 2 electrons per shape

F orbitals

Summary of Orbitals

s

p

d

f

# of shapes Max electron Starts at energy level

1 2 1

3 6 2

5 10 3

7 14 4

By Energy Level

• Orbitals do not fill up in a neat order.• Energy levels overlap• Lowest energy fill first.

Electron Configuration

• Way electrons are arranged in atoms.• Aufbau principle- electrons occupy the

lowest-energy orbital that can receive it. This means electrons enter the lowest energy first.

• This causes difficulties because of overlap of orbitals of different energies.• Pauli Exclusion Principle- states

that no 2 electrons in the same atom can have the same set of four quantum numbers. Basically, at most there are 2 electrons per orbital with different spins.

• Hund’s Rule- Orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron. • This means when electrons occupy

orbitals of equal energy they don’t pair up until they have to. • (BUS RULE)

Valence Electrons, Lewis Dot Structures,Electron Configuration

& Orbital Notation

• Get out your periodic table and follow along on the handout