Atomic orbitals are fundamental to the atomic orbital
model (also called
the wave mechanics model or electron clouds), and provide a framework for visualization of the
behavior of electrons. This model does not predict the exact location of the electrons but provides areas
that electrons are most likely to be located in what is called an "electron cloud". Multi-electron atoms are built up from
this model and provide an overall view and predictor of the properties of the atom. Repeating periodicity
of blocks of 2, 6, 10, and 14 within the periodic table are due to the total number of
electrons in a completed set of s, p, d and f atomic orbitals.
The nucleon is represented as a circular shell.
The first two electrons will align themselves on opposite sides of the proton, repelling
each other. Since the electrons do not feel the proton pull inside the shell, they end on the edge of the shell.
Over a short period of time, they align their spin with the proton, forcing the magnetic poles of the two electrons
to face each other. These two electrons have opposite spins, face each other, and are the two members of the
1s energy level.
An electron
can be thought of as a closed current loop that has trapped an orthogonal
magnetic field. Two circular current loops, located one above the other, with parallel planes,
will attract each other, independent of the trapped magnetic field. Electrons pair up and combine their trapped magnetic fields,
resulting in "bonded" electrons and lowered energy.
In an element, this causes electrons to "stack up", where level-2s electrons will find a spot directly "above"
the level-1s electrons relative to the center of the nucleon. For a teaching example of the attraction of two current loops using Ampere's law,
Click Here.
The six level-2p electrons, are at a slightly lower energy
compared to the level-2s electrons and form a criss-cross pattern across the center of the nucleon. This
pattern when viewed directly above one of the level-2p electrons, shows one electron directly below and the other four level-2p electrons forming
a precise x/y grid. Next, the two level-3s electrons stack on the level-2s electrons and the six
level-3p electrons stack on the level-2p grid. Although not discussed here,
the next ten electrons are level-3d electrons and fill the 10 "holes" in the 18 electron Argon grid.
Simple bonding - Ortho and Para Hydrogen
Bonding between elements occurs
when an electron, trapped in an energy level of one element, gets trapped in an energy level of
another element, thereby binding the two elements together.
A hydrogen proton and an electron and is neutral in charge.
Although neutral, the proton acting as a shell of charge with the electron close to the edge of the
shell, will attract other neutral hydrogen atoms until one electron (or perhaps 2 in the ortho form)
is trapped in both hydrogen shells binding them together. An electron trapping two protons together
is called a para-bond and where two electrons trap two protons together, it's called an ortho-bond.
Click here to try playing a game
where you aim and shoot an electron at other electrons bound to hydrogen protons. You see the effect
of electrons interacting with other electrons and protons over attosecond (10^-18) timeframes and
sub-nanometer (10^-9) distance scales.
Valence Electrons, bonding and Hybrid Orbitals
Electrons in the outer shell are called "valence" electrons and are
available for bonding. A shell of electrons that is one short, is said to have a "hole" in that spot.
This attracts nearby electrons that may not yet be magnetically paired.
This is modelled as a red dot (electron) filling a larger black circle (the hole).
Bonds are formed by the overlapping of holes and electrons.
Hybrid orbitals form and stableize if the heavy nucleons temporarily form
particular patterns. Electrons fill in the holes of an unstable pattern and over time stable hybrid orbitals
form.
like the sp orbital form when, for example in Fluorine, the 2pz orbital is available for bonding
(the hole shown as a black spot) as is the 1s orbital of hydrogen (also in black). An electron
in the level-2p hole of the Fluorine atom from the hydrogen atom, and an electron in the level-1s
hole of the Hydrogen atom from the Fluorine atom, form a covalent bond between Hydrogen and Fluorine.
Using a model called "Valence Bond Theory" to describe bonding molecules.
Any spots missing electrons, can be considered "holes" that will attract an electron. This
attraction forms the basis of bonding.
sp, sp2, and sp3 hybrid orbitals
In this model,
bonds are formed by the overlapping of two atomic orbitals on different atoms. Hybrid orbitals,
like the sp orbital form when, for example in Fluorine, the 2pz orbital is available for bonding
(the hole shown as a black spot) as is the 1s orbital of hydrogen (also in black). An electron
in the level-2p hole of the Fluorine atom from the hydrogen atom, and an electron in the level-1s
hole of the Hydrogen atom from the Fluorine atom, form a covalent bond between Hydrogen and Fluorine.
