Atomic structure (Structure of the atom (Atoms contain equal no. of…
All substances are made up of atoms
There are 100 types of different natural atoms
The periodic table lists all the elements on groups and periods
It is important to have symbols so different nationalities can understand.
Elements put in groups (columns) contain similar properties to each other.
A stair case can be drawn under Boron to separate metals and non-metals. Elements on the left are metals.
Silicon and Germanium are semi-metals and only have some metallic properties
An element is one type of atom
Elements such as Silver, Chromium, Copper and Gold are shinny.
Oxygen, Nitrogen, Aragon and Chlorine are non-metals and are gasses at room temperature
A compound is more than one type of atom
Chemical bonds hold the atoms tightly together
An atoms has a tiny nucleus that contain protons and neutrons surrounded by rings with electrons on
No new atoms are ever created or destroyed
Therefore the mass of reactant = the of product
There are the same no. of atoms of each side of the equation
EG: H2 + O= H2O
This can appear to be untrue in lab experiments.
EG: when you heat calcium carbonate the masses will be different before and after. This is only because the CO2 has floated away however.
state symbols include extra information:
aq= in water
A mixture is made up 2 or more substances that are not chemically combined
Mixtures cab be separated by
Used to separate insoluble substances from soluble substances. This is most commonly used with filter paper.
EG: coffee been from water
Used to obtain a pure salt. To do this you need to heat the salt solution over a water bath until little crystals start to form around the edges.Then evaporate the solution at room temperature
EG: Removing salt from water
Separate a soluble sold from a solvent while keeping the solvent. Heat and boil a solution but direct the gas into a condenser to turn it back into a liquid. Any solid swill stay in the flask whereas the water is now kept.
EG: countries with a lack of fresh water
Compounds and Mixtures
Separated more easily
No fixed composition
No chemical bonds between atoms
Chemical bonds between atoms
Only chemical reactions can separate compounds
Fractional distillation and paper chromatography
Fractional distillation is a way of separation liquids using a fractionating column.
You use this method on miscible liquids (ethanol and water).
Miscible means the liquids dissolve together unlike water and oil
Miscible liquids have different boiling points
You cant just boil of a liquid though because they all give of vapour before their boiling points
To help this you can add a fractionating column. The vapour will pass over and between the glass beads in the column.The substances with a higher boiling point will condense more readily on the bottom of the columns as the temperature falls as you go up the column.
Paper chromatography separating dissolved mixtures using chromatography paper.
This works because some compounds dissolve better than others.
A capillary tube is used to add spots of the solution on paper
The paper is then placed so the end is in water. The water will then soak up running through the spots and pulling them up.
The more soluble the solution is the higher up it will go.
History of the atom
Ideas about the atoms has changed over time
The Greeks first had ideas about arranging atoms in the 1800's
thought that substances were tiny little hard shells. He also thought that they could not be broken.
discovered in the late 1800's electrons. He did this by applying high voltage to gasses at low pressure. He proposed a new idea that the electrons were embedded in a cloud of positively charged smoke. He said this because he knew the atoms were neutral so something had to balance out the electrons.
(evidence for electrons)
later said that the negative charge must be in a concentrated area not smoke.He said this because Geiger and Marsden results when doing experiments with radioactive particles results shocked them.
(Evidence for nucleolus)
was the next to revise the atom structure. in 1914 he noticed that light was given out when atoms were heated. He knew that the electrons must be circling around the nucleolus.
Structure of the atom
The relative mas of a proton and neutron is 1
Protons have a +1 charge
Electrons have a -1 charge
Neutrons have no charge
Atoms contain equal no. of protons and neutrons
This means their overall charge is almost 0 (it would take about 2000 to create a mass of 1)
Atomic no. = no. of proton or electrons
Mass no. = no. of proton (or electrons) + no. of neutrons
Irons, atoms and isotopes
If and atom loses a electron the become positive ion
This is because the no of proton is now greater than the the no of electrons
Isotopes are the same as atoms but with a different no. of neutrons. They have the same properties but stuff like mass can differ.
The extra neutrons can make the atom radioactive
Some can also be denser
There are 7 billion billion billion atoms in the human body (7,000,000,000,000,000,000,000,000,000)
each atoms is 10 billionth of a metre across (0.000000001 m)
The no. of electrons on the outer shell determinism which way the the atom will react.
The inner shell has the least energy . Energy the increases as the shell gets further sway from the centre