Chemistry Atomic Structure

Mixtures are made of 2 or more substances (elements and compounds) that aren't chemically combined. They can be seperated and their properties don't change because they have been mixed with another substance. 

Chromoatography: It seperates solutions with a number of different solutes (solids) in the solvent (liquid). Place a drop of the solution to be seperated near the bottom of a piece of chromoatography paper. Dip the bottom of the paper in a solvent. The solvent will move up the paper, carrying the solutes in the solution with it. Different solutes move at different speeds, so they seperate. 

Filtration: Seperates mixtures of insoluble (can't dissolve) solids and liquids. Pour mixture through filter paper, the insoluble solid is trapped and the liquid runs through the paper and collected below. 

Crystallisation: Seperates solution into their different parts, dissolved solutes and and solvents. Heat the mixture up so that the solvent evaporates. Eventually, crystals of the dissolved solids (solutes) will form. You can collect the solvent (liquid) by condensing it as it evaporates. 

Simple Distillation: Seperates 2 liquids with different boiling points, the mixture is heated until the liquid with the lower boiling point starts to boil. The vapour released passes through a condenser, where gas cools back to a liquid. 

Fractional Distillation: Seperates lots of liquids with different boiling points, the mixture is slowly heated until the liquid with the lowest boiling point boils and condenses. We increase the temperature slowly to collect the other fractions. 

Plum Pudding Model: In 1897 J.J. Thompson discovered electrons. He modelled them as the 'Plum Pudding' with a ball of positive charge (dough), with negatively charged electrons (currents) mixed in with the 'dough'. 
Rutherfords Nuclear Model: In 1909, Rutherford discovered that alpha particles could bounce back off atoms. He concluded that an atom's mass is concentrated in the atoms centre. This was the "nucleus" and contained positively charged particles called protons.
The Modern Model: Bohr discovered that electrons orbit the nucleus at fixed distances. In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all, and named them neutrons. 

Protons (+1): Found in the nucleus, element's atomic number is the number of protons it has. 
Electrons (-1): Orbit the nucleus, number of electrons equals number of protons.
Neutrons (0): Found in the nucleus. 

Atoms: Relative Mass = number of protons + number of neutrons. Have an average radius of 0.1nm. 

Rows in the periodic table are called 'periods'. Columns are called groups, the group number is equal to the number of electrons an atom has in its outer shell. Elements in a column have similar chemical properties, they react in similar ways. Newlands periodic table was in order of the weight of the element. Although, the table was incomplete and some elements were placed in inappropriate groups. Mendeleev's periodic table realised there was still undiscovered elements. He added gaps to Newlands' table for these elements. Predicted properties of undiscovered elements. The modern periodic table shows that Mendeleev ordered elementd by atomic number, so the modern table is very similair but with the gaps filled. 

Metals are found on the left side of the periodic table because they have fewer electrons in their outer shell. When they react, they lose 1 negative electron to become positively charged. Metals have high melting points, they are good conductors of heat and electricity and they are all solids. 
Non-metals are found on the ride side of the periodic table because they have more electrons in their outer shell. When they react, they either gain electrons to become negatively charged or they share electrons to become neutral molecules. Properties are low melting and boiling points, often found as gases and do not conduct electricity or heat. 

Atoms with the same element and different number of neutrons are called isotopes. There are 3 forms of hydrogen: Protium, it has 1 proton and 0 neutrons. It is used in fuel cells and production of plastics. Deuterium, it is hydrogen with 1 proton and 1 neutron. It is used in nuclear fusion. Tritium is a hydrogen atom with 1 proton and 2 neutrons, it is used in thermonuclear fusion weapons. 

Relative atomic mass is the average mass of all of the isotopes of an element. 

Elements in group 0 are unreactive because they already have a full outer shell. They do not need to lose or gain electrons. Can be used in lightbulbs because the noble gases will not react with the hot metal filament. They are monatomic, so they exist as single atoms instead of forming molecules. They have low boiling points, but it does increase the further down the group becuase relative atomic masses increase further down. They have a low density, but it does increase the further down the group because of increasing relative atomic masses. 

Halogens have 7 electrons in their outer shell, they gain 1 electron when the react to have a full outer shell and become negative ions. They are diatomic molecules when they share electrons. When a metal atom transfers its outer electron to a non-metal atom, salts are formed. Result is a compound, ions all have full outer shells. They get less reactive as you go down the group because: the atoms gain more electron shells. The outer electron shell is further from the nucleus and the attraction between the electron and nucleus decreases. 

Displacement reactions, a more reactive halogen will displace a less reactive halogen from a compound. 

Elements in group 1 are called Alkali metals, they have one outer electron which us usually given away in chemical reactions. Lithium is the least reactive of Alkali metals, it burns with a red flame and reacts with oxygen. Sodium is more reactive than Lithium because its outer electron is less strongly attracted to the positively charged nucleus. Potassium is more reactive than both because its outer electron is the least attracted to the nucleus, it burns with a lilac flame. 

When reacting with chlorine, a metal chloride is formed which dissolved in water to give a colourless solution. When reacting with water, it melts to create a metal hydroxide. When reacting with oxygen, it rapidly turns from silverly shiny to dull as a metal oxide is produced.