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The History of chemistry
Chemistry started around the prehistoric times (the beginning of the Christian Era.) 
In 430 BC an Ancient Greek philosopher named Democritus claimed that matter is made up of little things called atoms. Democritus named this the ‘atomic theory of the universe’. 
Later in 300 BC Aristotle (also an Ancient Greek philosopher) announced the existence of 4 elements; Fire, Air, Earth and Water. He decided that all matter consists of these of these elements and that matter had four properties; hot, cold, dry and wet. At the end of the 17th century many alchemists who were greatly convinced by Aristotle’s theory, tried to change cheap metals into gold. The substance used for this conversion was called the “Philosopher’s Stone.” When the 17th century ended Aristotle’s theory of elements proved to be wrong.
From the 13th century to the 15th century Pope John XXII prohibited gold-making but it continued regardless. Alchemists also wanted to find a chemical mixture that would help people live longer and cure all illnesses. They called this the ‘Elixir of life’ however it was never discovered. 
At the end of the 17th century to the mid of the 19th century Charles Coulomb discovered using a torsion balance that two charged particles separated by a distance. Have a repulsion (force pushing particles apart) or attraction (force pulling the particles towards each other) directly proportional, to the product of their two charges or inversely proportional to the square of the distance between them.
Joseph Priestley, an English chemist, discovered carbon dioxide and oxygen by heating mercury in 1774 to 1794. He collected colourless gas by burning different substances. He called this gas ‘Dephlogisticated gas’ which we now know as oxygen. Antoine Lavoisier ( known as the “Father of Chemistry”) proved the Phlogiston theory wrong and renamed this gas ‘oxygen’. He also realised oxygen gas was not the only component of the air around us.
In 1803 John Dalton published his Atomic Theory which states that matter, is made up of atoms, atoms are very small and invisible,
In 1954 Heinrich Geisser made a vacuum tube. Due to the vacuum tube creation William Cordes discovered cathode rays which have a coating of zinc sulphate. When electricity is passed through the apparatus an image appears and the zinc sulphate glows. 
In 1897 J.J. Thompson placed a Crookes tube under 
a magnetic field where he found a negative charge. He theorised that all atoms had this charge. Thompson later received a Nobel Prize for this work. 
In 1885 the proton was discovered by Eugene Goldstein using a tube filled with hydrogen gas to find only positive particles. 
Marie Curie discovered uranium and thorium in 1897 and Ernest Rutherford (a kiwi physicist) discovered three types of radioactive decay when he tried to send decaying particles through a magnetic field. Some particles deflected to the positive side, some to the negative side and some did not deflect at all. These three types of radioactive decay are called alpha particles (+), Beta particles (-) and gamma rays (neutral). From this experiment he was able to create the ‘Rutherford Model’. The Rutherford model is a model by Ernest Rutherford, where the protons and neutrons are in the center and the electrons are moving around the protons and neutrons but the electrons are not apart of the nucleus. 
In 1932 James Chadwick discovered the neutron and Enrico Fermi bombarded elements with neutrons. James Chadwick decided to look for a neutral charged particle, as positive particles and negative particles had been discovered. His experiment included projecting alpha particles towards Beryllium. The particles released from Beryllium were uncharged.  
After the neutron, Irene Curie and Frederic Joliot-Curie discovered radioactive elements. They did this by exposing aluminum foil to alpha particles, when the radioactive source was removed they discovered that aluminium became radioactive. 
In chemistry it started with only only the four elements; fire,earth,water and air and it progressed over time to electrons,protons,neutrons and elements like Lithium. Due to these discoveries we understand more about the world we live in.

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Symbols, Atoms and The Periodic Table
The periodic table of elements currently has 118 elements. The first elements to be discovered were Copper, Sulfur, Silver, Tin, Antimony, Gold, Mercury and Lead. These elements were found in Ancient times. 
The periodic table was mainly developed by Mendeleev, a Russian chemist who advanced the periodic classification of elements. He found out chemicals are arranged in order of increasing atomic weight. The resulting table displayed a recurring pattern of properties within groups of elements. Other people like; John Newlands, Alexandre Béguyer de Chancourtois and Julius Lothar Meyer made important contributions to the first Periodic Table, but Mendeleev was the main contributor to the table. As only 60 elements had been discovered at the time, and some of the information of these elements were wrong so it was very hard to figure out the proper information of the elements.
Atomic Models over the years 
Democritus/Dalton’s Model:
The very first atomic model was made by Democritus, who thought matter consisted of invisible particles called atoms and a void (empty space). He stated that all atoms are unchangeable and that all atoms have no internal structure. His atomic model was solid, and stated all atoms differ in size, shape, mass, position and arrangement, with an empty space between them. He developed this theory by reasoning rather than science. Democritus around 400BC, composed this idea while Dalton (1803-1805) advanced the model in more depth.
Thomson’s Model (1897):
JJ Thomson discovered the negative charge of an electron. Thomson assumed that an electron is two thousand times lighter than a proton and believed that an atom is made up of thousands of electrons having the negative charge. In his model, he presumed atoms have a cloud of negative charge and positive charges. This theory is also named “Plum Pudding” model as atoms are thought to be large positively charged sphere with electrons embedded in it. This reminded him of a plum pudding as the plums are embedded in the pudding.
Rutherford’s Model (1911):
Ernest Rutherford tested Thomson’s model using his famous gold foil experiment. The gold foil experiment is an experiment, where positively charged alpha-particles are shoot through a very thin piece of gold foil, behind the gold foil is a screen of zinc sulfate.
Of course, Thomson’s model was proved to be wrong, as expected, most particles went right through the gold foil. Rutherford discarded Thomson’s model and decided to remake Thomson’s theory. Rutherford reasoned that the only way the particles could be deflected backwards was if the mass in an atom was concentrated in a nucleus. He then developed his model of the atom which puts all the protons in the nucleus and the electrons in an orbit around the nucleus, like the planets orbiting the sun.
1)Picture: https://www.ck12.org/chemistry/gold-foil-experiment/lesson/Rutherfords-Atomic-Model-MS-PS/
Bohr’s Model (1913):
Ernest Bohr’s Model is a remake of Rutherford’s model, but more correct than Rutherford’s. Bohr’s Model does contain some errors, but we still use it today. In Bohr’s Model the electrons orbit the nucleus, the energy of the orbit is related to its size and the lowest energy is found in the smallest orbit. Radiation is absorbed/emitted when an electron moves from one orbit to another. The atom also has outer shells. 
2)Picture: http://morgancampenschemistry.blogspot.cz/2014/01/atomic-models.html 
Reactions+Equations 
There are six types of reactions;
Combustion reaction;
Combustion happens when something burns. Combustion takes place when carbon and hydrogen react with oxygen to produce water vapour, heat and carbon dioxide.
For example; when magnesium reacts with oxygen it produces a very bright, white light and heat.
Synthesis Reaction
A Synthesis Reaction happens when simple compounds are combined to make an even more complex compound.  
Like photosynthesis; Carbon Dioxide + Water + Light = Oxygen + Glucose  
Combustion reaction 
A combustion reaction is when a molecule breaks apart into similar molecules. 
Like burning wood; Glucose + Oxygen = Carbon dioxide + Water 
Displacement reactions are types of reactions where one reactant is replaced by another reactant. 
There are two types of displacement reactions; 
A Single displacement reactions: reactions where one reactant(a substance that changes during a reaction)  is replaced by apart of another reactant. 
For example, AB + C = AC + B
3)Picture: http://www.wakadeclasses.com/types-of-chemical-reaction/ 
A Double displacement reactions: are reactions where the cations(ions that have a positive electrical charge) and anions(ions that have a negative electrical charge) in the reactants switch partners to form products. For example, 
AB + CD = AD + CB 
4)Picture: https://socratic.org/questions/how-do-you-recognize-a-double-displacement-reaction 
Base reaction also known as ‘neutralisation reaction’
Acid-base reaction happens when you combine an acid with a base, you get water and something else. This reaction is very similar to a double displacement reaction. For example; HA + BOH = BA + H2O 
How to tell which reaction is which?
If the equation contains carbon dioxide, water and oxygen then its combustion 
If it’s something simple made into something complex, then it’s synthesis.
If it’s something complex broken apart then it’s decomposition
If the elements are pure then it’s single displacement 
If water is a product of this reaction then it’s an acid-base reaction. If not then it’s a double displacement reaction.   
Chemical Equations
Balanced chemical reactions show what happens to different atoms in reactions. 
For example; copper + oxygen = copper oxide 
Chemicals ending -ide= non-metal+metal
Chemicals ending -ate= non-metal+metal+oxygen
For example; sulphur + iron + oxygen = iron sulphate 
Copper and oxygen are the reactants as they are on the left (two substances being mixed together) and copper oxide is the product as it’s on the right (what copper+oxygen produced) 
In a chemical word equation, it would look like this;
Cu + O2 = CuO 
The equation above is an unbalanced equation as there’s 2 molecules of oxygen on the left and only one molecule of oxygen on the right. That’s why you need to balance it by putting a big number in front of the reactant that’s unbalanced;
2Cu + O2 =  2CuO
Chemical Formulas   
Chemical Formulas show how many atoms are joined together which makes up a type of compound. For example; iron sulphate. Every iron atom is joined to one sulphur atom. 
Ionic Bonding
Ionic Bonding is compounds formed from metals and non-metals that consist of ions. The ionic bond is the force of attraction between the oppositely charged ions. This shows how ions are formed when sodium atoms react with chlorine atoms to form sodium chloride.
For example; Chlorine has 7 electron on its outer shell and Sodium has 1 electron on its outer shell, Chlorine wants a complete shell (which is 8 electrons) so Sodium loses 1 electron and Chlorine gains 1 electron. 
5)Picture: http://www.physicsandmathstutor.com/chemistry-revision/ionic-bonding/ 
Covalent Bonds
Covalent Bonds are compounds that are formed from non-metals that consist of molecules. The atoms in a molecule are joined together by covalent bonds. These bonds form when atoms share the same pairs of electrons.
For example; CO2  is carbon dioxide which means, two oxygen atoms are connected with one carbon atom
6) Picture: http://chemistry.tutorvista.com/inorganic-chemistry/covalent-bond-examples.html
 Elements 
The elements in the periodic table are arranged into periods; which go across. The elements that are in the same periods have the same atomic orbital. The elements are also arranged in groups, groups go down the periodic table. Groups show the number of electrons on the outer shell, like group one have one electron, group 2 have 2 and so on. Hydrogen and Helium are special elements. Hydrogen,in its neutral form, does not have a neutron. Hydrogen has one proton and one electron, so Hydrogen wants to bond itself to other elements to fill its outer shell. That’s why in chemistry we use H2 for Hydrogen, two Hydrogens atoms make up a full outer shell. 
Helium is different from all of the other elements. It is very stable with only two electrons in its outer orbital. Even though it only has two electrons, it is still grouped with the noble gases (they have 8 electrons in outer shell.) The noble gases and helium are all “happy,” because their outer shell is full.
Group 0-Noble Gases 
The Noble Gases all have eight electrons on their outer shell apart from Helium, as Helium is different (has only two electrons on its outer shell).  
Their reactivity increases as you go down the group. 
Group 1-Alkali Metals 
The Alkali Metals all have one electron on their outer shell. Their reactivity increases as you go down the group. The density also increases as you go down the group and the melting point/boiling point.  
Group 2-Alkaline Earth Metals 
The Alkaline Earth Metals have two electrons on their outer shell. Their reactivity increases as you do down the group. Their reactions are slower than group one. 
Group 3- The Icosagens 
The Icosagens all have three electrons on their outer shell. Reactivity increases as you go up the group. 

Group 4- The Crystallogens 
The Crystallogens all have four electrons on their outer shell. Reactivity increases as you go up the group.
Group 5- The Pnictogens 
The Pnictogens all have five electrons on their outer shell. Reactivity increases as you go up the group. 
Group 6-The Chalcogens
The Chalcogens have six electrons on their outer shell. Reactivity increases as you go up the group. 
Group 7- The Halogens 
The Halogens have seven electrons on their outer shell. Their reactivity increases as you move up the group.
7)Picture: https://play.google.com/store/apps/details?id=jqsoft.apps.periodictable.hd
Acid, bases and the pH scale
8) Picture: http://resumess.radiodigital.co/ph-scale/ 
The pH scale is a scale from 1 to 14 showing the measure of acidity or alkalinity of water soluble substances. Seven is the neutral point. 7 and under means the substance is acidic, 1 being the most acidic. 7 and above means the substance is alkaline, 14 being the most alkaline. To put it in perspective, the majority of foods are acidic, while everyday cleaning products are alkaline and pure water is neutral (7) on the pH scale. The pH in the pH scale stands for the ‘potential of Hydrogen.’ 
Water is neutral on the pH scale because, in water a small amount of molecules separate. So this means some of the water molecules lose a Hydrogen and they become Hydrogen ions (H+) (every water molecule has two Hydrogen molecules and one Oxygen molecule.) As the water molecules loses Hydrogen, the water molecules reduced in amount and form Hydroxide ions(OH-). This is why water has a pH of 7 as water has an equal number of Hydrogen ions and Hydroxide ions. 
An acid is >7 so there are more Hydrogen ions than Hydroxide ions in acidic solutions. This is because when an acid is dissolved in water the balance between Hydrogen ions and Hydroxide ions is upset. 
An alkaline is <7 so there are more Hydroxide ions than Hydrogen ions. This is because when alkali is dissolved in water the balanced between both ions is upset as alkali soaks up the Hydrogen ions which means less Hydrogen ions. A strongly acidic solution has one hundred trillion times more hydrogen ions than a strongly basic solution. 9)Picture: https://blackafrohair.wordpress.com/tag/chemistry/ Automatisation Hydrogen ions are produced in pure water by the ionization (gaining/losing electrons to become ions) of a small percentage of water molecules.  For example; H2O = H+ +OH- Ionization makes the same numbers of hydrogen ions and hydroxide ions.  States of matter There are 3 main states of matter; solid, liquid and gas.  Solid particles are;  Strongly attracted to each other They are not compressible  They vibrate in place  They don't move around  They are in a regular pattern  Liquid particles are;  Not in a regular pattern They can move around  They are not very compressible  They take the shape of their container  Are strongly attracted to each other Gases are;  Compressible (compress means that the substance/thing can be squashed. You can compress a substance in its gas state but not in liquid or solid state) The forces of attraction between the particles are weak  The particles move fast in every direction  There's no regular pattern.  All of these substances expand on heating and contract on cooling. The particle theory explains how substances behave in the solid, liquid and gas state.  Changing States When a substance changes from one state to another, it's particles don't change, all that changes is the distance between the particles, their speed and the attraction between the particles.  For example; When a solid ( ice) melts it becomes a liquid ( water.) When that liquid evaporates it becomes a gas (steam). When that gas condenses it becomes a liquid and when that liquid freezes it becomes a solid.  Boiling Point=The temperature that a substance boils is its Boiling Point. Melting Point= The temperature that a substance melts is its Melting Point.  Substances If a substance has a sharp melting point, it is not mixed with anything else so it's called a pure substance, like water. If a substance melts over a range of temperatures then it is a mixture of substances.  Dissolving   A solution is a substance made from two or more substances that can dissolve in liquids. Solute is the substance that is dissolved in a solvent (a substance that dissolves the solute). For example; sugar and coffee powder dissolving in water, water is the solvent and sugar + the coffee powder are the solutes. Solubility Solubility is the mass of a solid that dissolves in 100g of water before becoming substance . The greater the mass of the substance dissolved in water, the more soluble the substance.