C1: Atomic Structure - Coggle Diagram
C1: Atomic Structure
Everything is made up of tiny particles called atoms. The nucleus is in the middle of the atom. It contains protons and neutrons which both have a relative mass of 1 .Most of the mass of the atom is concentrated in the nucleus. Electrons move around the nucleus in shells. They are negatively charged while protons are positively charged and have as en extremely small relative mass.
Atom are neutral because they have the same nuber of protons and electrons. In an ion, the number of protons do not equal to the number of electrons. An ion is a chraged atom.
In nuclear symbols the atomic number (top number) tells you how many protons there are. The Mass number (bottom number) tells the total number of protons and neutrons. Mass number is usually bigger than the atomic number
The number of protons decide what type of an atom it is. For example, an atom with one proton in its nucleus is hydrogen and an atom with two protons is helium. If a substance has all the same type of atoms, it is called an element.
An isotope is a different form of an element which has the same number of protons but different number of neutrons. So they have the same atomic number but different mass numbers.
Relative atomic mass= sum of (sum of isotope x isotope mass number) / sum of abundances of all the isotopes
Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calc the relative atomic mass of copper.
(69.2 x 63) + (30.8x65) / 69.2 +30.8= 63.616
Compounds are made up of different types of atoms bonded together. The atoms of each element are held together by chemical bonds. Making bonds involves atoms giving away,taking or sharing electrons .
Filtration is used to separate an insoluble solid from a liquid.
Filtration works because the filter paper has tiny holes or pores in it. These are large enough to let small molecules and dissolved ions through, but not the much larger particles of undissolved solid.
Crystallisation is used to produce solid crystals from a solution. When the solution is warmed, some of solvent evaporates leaving crystals behind. For example, crystallisation is used to obtain copper sulfate crystals from copper sulfate solution.To obtain large, regularly shaped crystals from crystallisation:
put the solution in an evaporating basin
- warm the solution by placing the evaporating basin over a boiling water bath or a bunsen burner
- stop heating when crystals begin to form around the edge of the
basin (the point of crystallisation)
- After the remaining solution has cooled down, pour the excess liquid away (or filter it). Dry the crystals using a warm oven or by patting them with filter paper.
Simple distillation is used to separate a solvent from a solution. It is useful for producing pure water from seawater.
Simple distillation works because the dissolved solute has a much higher boiling point than the solvent.
The solution is heated and the part of the solution that has the lowest melting point evaporates first.The vapour is then cooled, condenses and is collected. The rest of the solution is left behind in the flask. The problem is that you can only use it to seperate things with very different bioling points.
Fractional distillation is used to separate different liquids from a mixture of liquids. It is useful for separating ethanol from a mixture of ethanol and water, and for separating different fractions from crude oil.Fractional distillation works because the different liquids have different boiling points. When the mixture is heated:
- You put your mixture in a flask and stick a fractionating column on top.Then you heat it.
- The different liquids will have different boiling points so will evaporate at different temps.
- The liquid with lowest boiling point evaporates. When the temperature on the thermometer matches the boiling points of this liquid it will reach the top of the column.
- Liquids with higher boiling points might also evaporate but the column is cooler towards the top so they will condense and run back towards the flask.
- When the first liquid has been collected, you raise the temperature until the next one reaches the top.
A mixture is made up of two or more substances (elements ro compounds) that are not chemically bonded together
This method can be used to seperate different dyes in an ink.
- Draw a line near the bottom of a sheet of filter paper in pencil because they are insoluble.
- Add a spot of the ink to the line and place the sheet in a beaker of water.
- The solvent used used depends on what is being tested. Some compounds dissolve well in water but others need ethanol.
- Make sure the ink isn't touching the solvent because you do not want it to dissolve in it. The solvent seeps up the paper, carrying the ink with it.
- The more soluble a substance is the higher it will be carried up the paper.
- The end result is a pattern of spots called a chromatogram.
History of the atom
John Dalton published his ideas about atoms in 1803. He thought that all matter was made of tiny particles called atoms, which he imagined as tiny spheres that could not be divided.
Nearly 100 years later, J J Thompson carried out experiments and discovered the electron. This led him to suggest the plum pudding model of the atom. In this model, the atom is a ball of positive charge with negative electrons embedded in it - like currants in a Christmas pudding.
In 1909 Ernest Rutherford designed an experiment to test the plum pudding model. In the experiment, positively charged alpha particles were fired at thin gold foil. Most alpha particles went straight through the foil. But a few were scattered in different directions
Because of this, scientists realised that most of the mass of the atom was concentrated in the centre of the atom and that the nucleus must be positively charged. Since most of the particles went through they realised most of the atom was empty space Rutherford also discovered protons which had the same charge as a hydrogen nucleus.
Bohr said that electrons orbiting the nucleus do so at certain distances called energy levels. Chadwick proved the existence os the neutron.
The model today of the atom is called the nuclear model.
The first and lowest energy level shell can hold two electrons while the second and third hold 8. One the third has been filled the fourth begins to fill up.