Quantum Mechanics models of an atom

Objectives

To briefly introduce the development of quantum mechanics

To give an idea of the quantum mechanics model of the atom;

To introduce the sub-nuclear particles

What are quantum mechanics?

What are mechanics?

Mechanics are the rules which explain the movement of objects;

Developed by Sir Isaac Newton amongst others;

The only explanations that existed before late 19th Century;

By this time we knew that they did not explain and so could not apply to the very small e.g. electrons and light.

Up till now you thought

Matter Forces and energy were differentLight moves as wavesMatter is made up of particlesForces hold together particles or transform

energy.

Actually

They’re all the same. Everything is made up of some sort of particle.

Quantum mechanics

Developed at the end of the 19th and beginning of the 20th century to describe the movement of the very small.

Fully formulated in the 1920s involving the work of many brilliant scientists.

Simplest possible explanations

The energy levels of electrons were shown to be particular amounts, and couldn’t be just any value.

Electrons and light show features of particles and waves.

Einstein postulated particles of light = photons.

The world of the very small is completely different from the world we know.

Planck

1900 quantum hypothesis of Max Planck Planck's hypothesis is that energy is radiated and absorbed in discrete "quanta," or "energy elements". According to Planck, each energy element E is proportional to its frequency ν:

E = hvwhere h is Planck's action constant. When electrons are excited they move between

energy levels giving out predictable amounts of energy. We may see these as spectra of light.

Spectra

Einstein

in 1905 Albert Einstein interpreted Planck's quantum hypothesis realistically and used it to explain the photoelectric effect, in which shining light on certain materials can eject electrons from the material. Einstein postulated that light itself consists of individual quanta of energy, later called photons

Bohr Somerfield Rutherford Model

In atomic physics, the Bohr model, devised by Niels Bohr, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity

Niels Bohr tied the invisible of the inside of the atom with the visible of the spectrum by calculating which wavelengths of light Hydrogen could produced based on his own orbital model

Bohr and Spectra

Electrons are normally present in their ground state i.e. when they are in the energy level they should be

When they are given energy and moved to a new energy level they are in excited state

Electrons moving back from excited to ground state give out energy as light

The amount of energy given out moving between energy levels corresponds to different wavelengths of light

Hence different atoms have different electrons so different spectra.

Bohr-Rutherford Model

Since the Bohr model is a quantum physics-based modification of the Rutherford model, many sources combine the two, referring to the Rutherford–Bohr model.

It’s special quality is that it can explain the different energy levels emitted in the spectra of Hydrogen

True quantum mechanics

In 1925 a new kind of mechanics was proposed, quantum mechanics in which Bohr's model of electrons traveling in quantized orbits was extended into a more accurate model of electron motion. The new theory was proposed by Werner Heisenberg. Another form of the same theory, modern quantum mechanics, was discovered by the Austrian physicist Erwin Schrödinger independently and by different reasoning

A more modern model of the atom

This shows electron cloudsThere are more than one in all energy levels above 1They are changed by bonding with other atomsThey show where an electron may be found

Everything is made up from little bits (material and energy and forces)

In Scriptures Jesus is often referred to as ‘the light’, and most believers focus on the metaphorical value of these statements. But as we realize that all forms of matter are in fact 'solidified' light (energy, as in E=mc2) and the electromagnetic force holds all atoms together, the literal value of Paul's statement "and He is before all things, and in Him all things hold together (Col 1:17)" becomes quite compelling.

Particles

Particles are either so-called real particles, also known as fermions,

or they are force particles, also known as bosons. (Currently made famous by the Higgs Boson particle being sought at Cern’s Large hadron collider) Now being referred to as “a particle God doesn’t want us to find.” – Or simply the “God Particle”

How does this fit what we know about atoms?

Quarks, which are fermions, are bound together by gluons, which are bosons. Quarks and gluons form nucleons (i.e. neutrons and protons), and nucleons bound together by gluons form the nuclei of atoms.

The electron, which is a fermion, is bound to the nucleus by photons, which are bosons. The whole lot together forms atoms. Atoms form molecules. Molecules form objects

Quanta Atoms Molecules Objects

What we’re made of?

Everything that we can see, from the most distant stars to the girl next door, or this computer you are staring at and yourself as well are made up from a Mere 3 fermions and 9 bosons. The 3 fermions are Up-quark, Down-quark and the electron.

The 9 bosons are 8 gluons and 1 photon.

Final thought

Individual quantum particles are subjected to a completely different law than the law to which large objects made from quantum particles are subjected.

We call this quantum mechanics

We will revisit the organisation of electron orbitals in much greater detail in 4th semester

If you want to know any more go read a book