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Chemistry Module 4-Atoms
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Chemistry Module 4-Atoms
Background
- Atom-a very small part of matter
- nucleus contains positive protons and neutral neutrons and is positively charged
- very heavy
- electrons revolve on the shells
- no mass,negatively charged
- the whole mass of an atom is in the nucleus
- electrons revolve on the shells
- very heavy
- their mass is about 10^-23g
- their radius is about 10^-10m
- mass number is the total no. of protons and neutrons
- atomic number is the number of protons
- no. of protons is equal to no. of electrons
- to get the number of neutrons, subtract the atomic number from the mass number
- no. of protons is equal to no. of electrons
- nucleus contains positive protons and neutral neutrons and is positively charged
- isotopes
- has the same atomic number but different mass number
- we change the different number of neutrons
- has the same atomic number but different mass number
- Atom-a very small part of matter
The history of the atom
- John Dalton described atoms as solid spheres and that different spheres made up the different elements
- One correct theory was that all matter is made of atoms
- In 1897 J J Thomson showed that this was wrong and that an atom contained smaller pieces
- discovered the electron
- This was known as the plum pudding model
- In 1909 Rutherford showed that the plum pudding model was wrong
- he used an experiment to show that an atom must contain a central nucleus
- with his assistants Geiger and Marsden
- in 1905 they tested the atom imagined as a sphere of positive charge with negatively charged electrons dotted around insided
- Beam of alpha particles was aimed at very thin gold foil
- they expected the alpha particles to pass straight through
- However, some emerged from the foil at different angles, some even deflected straight back and some passed through
- they realised that the positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom
- They concluded, most of the atom is an empty space
- some particles were repelled by the nucleus
- most of the atoms mass is concentrated in the central nucleus
- nucleus surround by a 'cloud' of negative electrons
- plum pudding replaced with nuclear model of atom
- nucleus surround by a 'cloud' of negative electrons
- most of the atoms mass is concentrated in the central nucleus
- some particles were repelled by the nucleus
- They concluded, most of the atom is an empty space
- they realised that the positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom
- However, some emerged from the foil at different angles, some even deflected straight back and some passed through
- they expected the alpha particles to pass straight through
- Beam of alpha particles was aimed at very thin gold foil
- in 1905 they tested the atom imagined as a sphere of positive charge with negatively charged electrons dotted around insided
- with his assistants Geiger and Marsden
- he used an experiment to show that an atom must contain a central nucleus
- Bohrs electron orbits
- he used experimental evidence
- to support the idea that electrons occupy particular orbits or shells around the nucleus
- therefore electrons in a 'cloud' would be attracted to nucleus
- but the atom would collapse?
- Therefore came up with a new model
- electrons only exist in fixed orbits or shells and not anywhere inbetween
- Tested by scientists
- helped to explain other observations and we know is now true
- more experiments, new evidence was found to fit the theory
- new evidence means new ideas
- make predictions which if proved correct are an indication that ideas are right
- Scientists put up their ideas for peer review
- other scientists can test and help develop
- Scientists put up their ideas for peer review
- scientific knowledge
- make predictions which if proved correct are an indication that ideas are right
- new evidence means new ideas
- each shell has a fixed energy
- Tested by scientists
- electrons only exist in fixed orbits or shells and not anywhere inbetween
- Therefore came up with a new model
- but the atom would collapse?
- therefore electrons in a 'cloud' would be attracted to nucleus
- to support the idea that electrons occupy particular orbits or shells around the nucleus
- he used experimental evidence
- In 1909 Rutherford showed that the plum pudding model was wrong
- This was known as the plum pudding model
- discovered the electron
- In 1897 J J Thomson showed that this was wrong and that an atom contained smaller pieces
- One correct theory was that all matter is made of atoms
- John Dalton described atoms as solid spheres and that different spheres made up the different elements
Ions
- ions are formed when atoms loose or gain electrons
- metal atoms form positive ions
- non-metal atoms form negative ions
- by gaining electrons
- group 6 gains 2 electrons
- group 7 gains 1 electron
- by losing electrons
- all of atoms in group 1 will lose 1 electron
- group 2 will lose 2 electrons
- group 3 will lose 3 electrons
- group 2 will lose 2 electrons
- non-metal atoms form negative ions
- metal atoms form positive ions
- ions are formed when atoms loose or gain electrons
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- Mind Map on Chemistry Module 4-Atoms, created by bashton on 03/03/2016.
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- bashton
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