163 Pages

## Elementary physics Edit

Highly recommend:
Thinking Physics Is Gedanken Physics by Lewis Carroll Epstein
Understanding physics by Isaac Asimov

Physics is all calculus. Trying to do physics without calculus is like trying to run a race on one leg.

If the position of an object as a function of time is given by

$position = p(t)$

then the velocity is given by

$v = \frac{dp}{dt}$

and the acceleration is given by

$a = \frac{dv}{dt} = \frac{d^2p}{dt^2}$

Velocity has units of distance per time (like miles per hour). Acceleration has units of distance per time per time.

The momentum of an object is equal to the mass times the velocity

$Momentum = m v$

The kinetic energy of an object is equal to half the mass times the velocity squared

$E = \frac{m v^2}{2}$

In the image below a red object of unit mass moving with velocity 2 strikes a blue stationary object with equal mass. The total horizontal momentum, total vertical momentum, and total energy are unchanged by the collision. In other words, energy and momentum are Template:Link.

 Before collision: Red object Horizontal momentum: 2 Vertical momentum: 0 Kinetic energy: 2 Blue object Horizontal momentum: 0 Vertical momentum: 0 Kinetic energy: 0 Total Horizontal momentum: 2+0 Vertical momentum: 0+0 Kinetic energy: 2+0 After collision: Red object Horizontal momentum: 1 Vertical momentum: 1 Kinetic energy: 1 Blue object Horizontal momentum: 1 Vertical momentum: -1 Kinetic energy: 1 Total Horizontal momentum: 1+1 Vertical momentum: 1+(-1) Kinetic energy: 1+1

A force of 1 Newton acting continuously on a mass of 1 kg will cause that mass to accelerate at 1 m/s2

$F = m a$
After the object has moved a distance of 2 meters it will have gained a kinetic energy of
$E = F \cdot distance = 1 \, Newton \cdot 2 \, meters = 2 \, Joules$

Gravity on Earth causes all free falling objects to accelerate downward at 9.8 m/s2

### Atoms Edit

External link: Periodic table at ptable.com

A red circle is an unpaired electron in the outermost shell.
A blue circle is a Template:Link of electrons.
Each electron shell is twice the radius of the previous shell.

 60px 60px

 60px 60px 60px 60px 60px 60px 60px 60px

 60px 60px 60px 60px 60px 60px 60px 60px

The next block of elements is more complex
A yellow circle is an unpaired electron in an inner shell.
 90px The unpaired electron in Potassium is a conduction electron. Conduction electrons are Template:Link.

 90px 90px 90px 90px 90px 90px 90px 90px 90px 90px

 90px 90px 90px 90px 90px 90px 90px

Copper is whats known as a Template:Link.

Zinc has a very low boiling point.

And the next block of elements is like it
A yellow circle is an unpaired electron in an inner shell.
 90px The unpaired electron in Rubidium is a conduction electron. Conduction electrons are Template:Link.

 90px 90px 90px 90px 90px 90px 90px 90px 90px 90px

 90px 90px 90px 90px 90px 90px 90px

Silver is whats known as a Template:Link.

Cadmium has a very low boiling point.

And the next block of elements is even more complex
A blue-green circle is an electron pair in an f-block subshell.
 120px The unpaired electron in Caesium is a conduction electron. Conduction electrons are Template:Link.

 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px

 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px

 120px 120px 120px 120px 120px 120px 120px

Gold is whats known as a Template:Link.

Mercury has a very low boiling point.

And the next block of elements is like it.
A blue-green circle is an electron pair in an f-block subshell.
 120px The unpaired electron in Francium is a conduction electron. Conduction electrons are Template:Link.

 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px

 120px 120px 120px 120px 120px 120px 120px 120px 120px 120px

 120px 120px 120px 120px 120px 120px 120px

Note: The metallic forms of the elements have electronic structures that differ slightly from the one the Template:Link predicts.

Each unpaired electron in the outermost shell (called the valence shell) forms a Template:Link with an unpaired electron in the outermost shell of a neighboring atom.

File:H2 shells.svg

Atoms that have no unpaired electrons in their valence shell are called Template:Link. Noble gases do not form chemical bonds and are therefore Template:Link.

 60px 60px 60px 90px 90px 120px

A single molecule of Template:Link consists of one Fluorine atom and one hydrogen atom and is therefore diatomic.
Fluorine is a powerful Template:Link. In fact, Fluorine is the most Template:Link element known. (It really likes electrons).
Fluorine is much more electronegative than hydrogen. This causes Hydrogen Fluoride to be a Template:Link.

File:HF shells.svg

A single molecule of Template:Link (H2O) consists of one oxygen atom and two hydrogen atoms.
Water is a polar molecule.

File:H2O shells.svg

A single molecule of Template:Link (NH3) consists of one nitrogen atom and three hydrogen atoms.
Ammonia is a polar molecule.

File:NH3 shells.svg

A single molecule of Template:Link (CH4) consists of one carbon atom and four hydrogen atoms.
Methane is a hydrocarbon. Hydrocarbons are non-polar molecules and therefore not soluble in water.
Methane is a gas. It boils at -161 °C.

File:Methane shells.svg

A single molecule of Template:Link (C2H6) consists of two carbon atoms and six hydrogen atoms.
Ethane is a gas. It boils at -88 °C.

File:Ethane shells.svg

A single molecule of Template:Link (C2H6O), also known as drinking alcohol, consists of two carbon atoms, six hydrogen atoms, and one oxygen atom.

File:C2H6O shells.svg

A single molecule of Template:Link (C8H18) consists of eight carbon atoms and eighteen hydrogen atoms.
Octane is a liquid. It boils at 125 °C.
If the chain were even longer and the hydrogen atoms were replaced with fluorine atoms then you would have Template:Link.

File:C8H18 shells.svg

But Benzene is a little bit different.
A single molecule of Template:Link consists of six carbon atoms and six hydrogen atoms arranged in a ring. Each carbon atom bonds with 2 other carbon atoms and with one hydrogen atom thus accounting for three unpaired electrons per carbon atom. But, as we already know, each carbon atom has four unpaired electrons so one electron per carbon atom is unaccounted for. There are six carbon atoms therefore a total of six electrons per benzene molecule are unaccounted for. Those six Template:Link form the blue circle around the molecule. See also: Template:Link, Template:Link, and Template:Link. Benzene molecules are shaped like flat plates. (See Template:Link.)

File:C6H6 shells.svg

A single molecule of Template:Link consists of five carbon atoms, five hydrogen atoms, and one nitrogen atom arranged in a ring. Six unpaired electrons form the blue ring around the molecule.

File:C5H5N shells.svg

Template:Link consists of carbon atoms densely packed in a regular hexagonal pattern:

320px

Template:Link consist of a two-dimensional hexagonal lattice of carbon atoms, bent and joined in one direction so as to form a hollow cylinder:

281px

150px
File:BF3 shells.svg
Its Boron atom has a vacant orbital which can form a covalent bond by sharing a lone pair of electrons on an atom in a base (in this case ammonia):[1]
File:BF3 reacting with ammonia.svg

A molecule of Template:Link consists of one Antimony atom and five Fluorine atoms.

File:SbF5 shells.svg
Its Antimony atom has a vacant orbital which can form a covalent bond by sharing a lone pair of electrons with a sixth Fluorine atom (actually its an ion) thus creating Antimony hexafluoride.
File:SbF6 shells.svg

Note that the molecule in the image above has a net negative charge of -1.

I would guess that the reason the six pairs of electrons are able to share the outer electron shell in antimony is because of sd5 Template:Link.