Ch. 4.2 Quantum Model of the Atom Atomic Structure

POINT > Recall Bohr’s atomic model POINT > Identify electrons as wave-like particles POINT > Define Heisenberg’s uncertainty principle POINT > Describe electron orbitals as three dimensional probabilities POINT > Describe how quantum numbers define electron orbitals

POINT > Recall Bohr’s atomic model Problem: Bohr’s model worked for hydrogen, but was inaccurate with atoms having more than one electron Bohr

POINT > Identify electrons as wave-like particles Light has wave-like properties Louis de Broglie showed that electrons also have wave-like properties de Broglie showed that electrons undergo diffraction and interference like waves (see p 98-99)

POINT > Describe Heisenberg’s uncertainty principle Heisenberg’s uncertainty principle: It is impossible to know the position and velocity of an electron Any attempt to locate an electron alters its path This is true for any atomic particle or photon

WB CHECK: What did de Broglie discover about electrons? electrons only exist at discrete energy levels the location and velocity of electrons is uncertain electrons undergo diffraction and interference electrons have a much smaller mass than protons

WB CHECK: What did Heisenberg tell us about electrons? electrons only exist at discrete energy levels the location and velocity of electrons is uncertain electrons undergo diffraction and interference electrons have a much smaller mass than protons

Erwin Shrödinger used mathematical models to describe electron motion POINT > Describe electron orbitals as three dimensional probabilities Erwin Shrödinger used mathematical models to describe electron motion Electrons are restricted to certain energy levels (supported Bohr) Electrons do not follow specific paths (unlike Bohr model)

POINT > Describe electron orbitals as three dimensional probabilities Shrödinger’s equations were the foundation of quantum theory The location of an electron is described as a mathematical probability in space The result is the electron cloud model of the atom

Electron cloud model of the atom POINT > Describe electron orbitals as three dimensional probabilities Electron cloud model of the atom Where the cloud is more dense, there is a higher probability of finding an electron (Usually drawn where electrons are ~90% of time)

Shrodinger’s equations WB CHECK: Shrodinger’s equations supported Bohr’s idea that electrons have discrete energy levels supported Bohr’s idea that electrons move on specific paths described electron orbitals as mathematical probabilities a and b a and c b and c

Models through Time… Quantum Mechanical (Electron Cloud Model)

Describes energy levels an electron can have POINT > Describe electron orbitals as three dimensional probabilities The quantum model: Describes energy levels an electron can have Describes an atomic orbital as a region of space with a high probability of finding an electron

POINT > Describe electron orbitals as three dimensional probabilities

Homework: Read pages 98-100 Pre-read pages 101-104 Atomic Spectra Lab Due Friday