Quantum Mechanical Model of Atom

Quantum Mechanical Model of Atom

by DESIREE JAWA, ETSS01

​Objectives:

• Understand the different atomic models that led to the formulation of Quantum Mechanical Model of atom.

• ​Explain how the Quantum Mechanical Model of the atom describes the energies and positions of the electrons.

Multiple Choice

It is the simplest or pure substance which contains the same type of atom.

• Element

• Compound

• Molecule

• Solution

Multiple Choice

What do you call the negatively charged subatomic particle?

• Proton

• Electron

• Neutron

• Nucleus

Multiple Choice

The uncharged subatomic particles with a mass approximately similar to protons are called ________.

• Neutrons

• Neutral

• Nucleus

• Isotopes

Multiple Choice

What is the nucleus of an atom composed of?

• Protons and Electrons 

• Neutrons and Electrons 

• Protons and Neutrons 

• Photons 

THE DEVELOPMENT OF

QUANTUM MECHANICAL MODEL​

• ​Bohr Model of Atom

• ​De Broglie's Wave-Particle Duality

• ​Schrödinger's Electron Cloud Model

• ​Heisenberg's Uncertainty Principle

​The Bohr Model of Atom

​Niels Bohr

​​- Danish physicist

​- Resolved Rutherford's Nuclear Model of Atom

​- Bohr assumed that the energies of the electron orbital were quantized.

​© University of California Museum of Paleontology's Understanding Science (http://www.understandingscience.org)

​The Bohr Model of Atom

Quantization of Energy

- Max Planck introduced the term "quantum" in the field of physics in the notion of "minimum amount of a quantity which can exist"

​- Electrons could only occupy particular orbits or

energy levels determined by the quantum of action.

​

​The Bohr Model of Atom

Quantization of Energy

​​Energy level or the principal quantum number is denoted by n with values 1, 2, 3, 4, ... ​​

or by letters K, L, M, N

​

​Electron capacity = 2n²

​​n = 1 ➡ 2 electrons

n = 2 ➡ 8 electrons

​ n = 3 ➡ 18 electrons

​ n = 4 ➡ 32 electrons

​The Bohr Model of Atom

​© LumenLearning.com

​Hydrogen Atomic Emission Spectrum

​The Bohr Model of Atom

Limitations to Bohr's Theory

​- It cannot be applied to multielectron atoms.

​- Orbits are not circular paths. Electrons do not follow a well-defined path, rather there is a cloud of probability (quantum mechanical model).

louis de broglie's theory

​- French physicist

- In 1924, he proposed the wave-particle duality of electrons

​Erwin Schrödinger's electron cloud model

​- Austrian theoretical physicist

​- In 1926, Erwin Schrödinger extended de Broglie's work by deriving what is today known as the Schrödinger equation. He used mathematical equations to describe the probability of finding an electron in a certain region in space, or orbitals.

concept mapping

Interactive Whiteboard Activity:

​Fill out the concept map by clicking this link:

https://app.nearpod.com/?pin=BEMXC

QUANTUM NUMBERS

The Principal Quantum Number ( n )

​The principal quantum number is an integer that determines the overall size and energy of an orbital. Its possible values are n = 1, 2, 3, ... and so on.

​©Chemistry LibreTexts. Atomic Orbitals and Quantum Numbers. (https://chem.libretexts.org/@api/deki/files/71006/CNX_Chem_06_03_Qnumbers.jpg?revision=1)

QUANTUM NUMBERS

The Angular Momentum Quantum Number ( l )

​The angular momentum quantum number is an integer that determines the shape of the orbital. The possible values of l are 0, 1, 2, ... (n - 1).

​© Angular Momentum Quantum Number. (https://study.com/cimages/multimages/16/angularmomentumshapes2.png)

QUANTUM NUMBERS

The Magnetic Quantum Number ( m_l )

​The magnetic quantum number is an integer that specifies the orientation of the orbital. The possible values of m_l are the integer values (including zero) ranging from -l to +l . For example, if l = 0, then the only possible value of ml is 0; if l = 1, the possible values of ml are -1, 0, and +1.

​©Protons Talk. Four Quantum Numbers. (https://protonstalk.com/wp-content/uploads/2021/08/Electron-Orbitals-as-per-Quantum-Numbers1-1024x601.jpg)

QUANTUM NUMBERS

The Spin Quantum Number ( m_s )

​The spin quantum number specifies the orientation of the spin of the electron. Electron spin is a fundamental property of an electron (like its negative charge). The orientation of the electron’s spin is quantized, with only two possibilities that we can call spin up ( m_s = +1/2) and spin down ( m_s = -1/2).

​©The Physical Significance of the 4 Quantum Numbers. (https://web.fscj.edu/Milczanowski/psc/lect/Ch8/SLIDE96.jpg)

QUANTUM NUMBERS

Summary

QUANTUM NUMBERS

PRACTICE

​Access this link: https://app.nearpod.com/?pin=TPVJX and fill the table with the correct quantum numbers.