AQA GCSE Chemistry C1 Atomic Structure Revision Notes .This page contains the detailed and easy notes for AQA GCSE Chemistry C1 Atomic Structure and Mixtures for revision and understanding Atomic Structure and Mixtures.
History of Atoms – Developments that has given the present structure of the atom
Present Structure of Atoms –Electronic configuration
Ions and Isotopes
History of Atoms
John Dalton
J.J Thomson
Rutherford
Neil Bohr
James Chadwick
Early 1800s
1800 end
1911
1914
1932
Discovered Atoms
Discovered Electrons
Discovered Nucleus
Gave the idea of Electronic shells
Discovered Neutrons
Plum Pudding Model
Alpha Scattering Experiment
Early 1800: John Dalton: Everything that has mass or volume is made up of atoms which is indivisible.
Late 1800: J J Thomsom: Discovered Atoms and Gave Plum Pudding model
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J Thomson took a glass tube and in this glass tube he kept a gas at a very low pressure.
The gas tube had a cathode and a anode and it was given a very high voltage around 150000V.
Thomson saw that the glass tube gave a green glow and it came from the rays that was given out of the cathode and he called these rays as cathode rays and as they were coming towards the positive terminal he concluded that these are the negative rays which are coming out of the gas atoms which are present in this glass tube, so he discovered the atom can further be divided and it has a negative and positive charge of Electrons with subatomic particles.
On the basis of that he gave this plum pudding model.
Plum pudding model says that atom is the sphere of the positive charge the positive charge is equally distributed and in this sphere of the positive charge the electrons are embedded as raisins and give the plum pudding model and according to him the electron the positive were similar therefore atom is neutral. Alpha Scattering Experiment – Geiger and Marsden –Radioactive particles Dense, positively charged particles (called alpha particles) were fired at the thinnest piece of gold foil. Most of the alpha particle passed straight through the gold atoms with their diffuse cloud of positive charge. Rutherford modify the structure of the J J Thomson and he said that the positive charge concentrated at the centre is the nucleus and he said that nucleus at the centre which is consisting of the positive charge elements atomic particles and then the electrons are revolving around this nucleus 1914: Neil Bohr– Idea of Electronic shells Energy given by atoms when heated had only specific amount of energy So Electrons are orbitiing at the specific energy levels called the electronic Shells 1932: James Chadwick – Discovered Neutrones Due to difference in mass of protons and the nucleus. Atomic Structure
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Structure of Atoms
Type of Sub Atomic Particle
Relative Charge
Relative mass
Position in the Atom
Electron
-1
1/2000
Around the nucleus in shells
Proton
+1
1
In the nucleus
Neutron
0
1
In the nucleus
No. of Proton, Neutron and Electron Banner 3
Atom is neutral so it has equal number of proton and neutrons
The number of protons in each atom of an element is called its atomic number.
The number of protons plus neutrons in the nucleus of an atom is called its mass number.
number of neutrons = mass number — atomic number
Electronic Configurations
Shell no.
I
II
III
IV
Max no. of Electron
2
8
8
18
For Example Sodium = No. of electron =2,8,1 Magnesium = 2,8,2 Banner 4
All Elements React to gain full outer shell
The number of electron in the outermost shell is the group number of the elements
Elements in the same group have same number of electron in their outer most shell
Element
Atomic Number
Configuration
Hydrogen
1
1
Helium
2
2
Lithium
3
2,1
Berylium
4
2,2
Boron
5
2,3
Carbon
6
2,4
Nitrogen
7
2,5
Oxygen
8
2,6
Fluorine
9
2,7
Iron
10
2,8
Sodium
11
2,8,1
Magnesium
12
2,8,2
Aluminium
13
2,8,3
Silicon
14
2,8,4
Phosphorous
15
2,8,5
Sulphur
16
2,8,6
Chlorine
17
2,8,7
Argon
18
2,8,8
Potassium
19
2,8,8,1
Sulphur
20
2,8,8,2
Ions – Charged atoms – unequal no. of proton and Neutrons Positive Ions – Loss of electrons
So more protons than electrons
Atoms gain positive charge equal to the number of electron lost
Na+ – +1 charge so lost one electron
Mg2+ – +2 charge as it has lost two electrons
Negative Ions – Gain of electrons More electron than proton Atoms gain negative charge equal to the number of electrons gained F– -1 charge as it has gained one electron 02- -2 charged as it has gained two electrons
11Na23
Na+
8O16
O2-
Proton
11
11
8
8
Neutron
12
12
8
8
Electron
11
10
8
10
11Na23
[13Al27]3+
[8016]2-
Atomic number
11
13
8
Mass Number
23
27
16
Electron Number
11
10
10
Proton Number
11
13
8
Neutron Number
12
14
8
Charge
0
+3
-2
Electronic Configuration
2,8,1
2,8
2,8
Isotopes
a) Members of the same elements
b) Have same atomic number but different mass number
c) Same number of electron and protons but different neutrons
d) Since electron numbers are the same they show similar chemical properties
e) They have different physical properties and radioactive properties.
Atoms — the smallest particle which consists of electron, protons and neurons
Proton – Positively charged sub-atomic particles which relative charge of +1, relative mass of 1 found in the nucleus of the atom
Neutron – Neutral sub—atomic particles with relative charge of O, relative of 1 found in the nucleus of the atom
Electron – Negatively charged sub-atomic particles with relative charge of -1, relative mass of 1/2000 found revolving around the nucleus in shells
Nucleus – The center of the atom which is positively charged and contains neutrons and protons.
Atomic Number – The number of protons in an atom
Mass Number – The number of proton and neutrons in an atom.
Ions – The charged atom with unequal number of protons and neutrons
Isotopes – Members of the same element with same number of electron and protons but different number of neutrons.
Positively charged subatomic particle Protons
Negatively charge subatomic particle Electrons
Electrons was discovered by J J Thomson
Neutrons was discovered by James Chadwick
Model given by J.J Thomson Plum Pudding Model
Q1 How to work out the neutron number of an atom ? Mass number – Atomic Number Q2 What do elements in the same group have in common ? They have same number of electrons in the outermost shell. For example, Sodium, Potassium both group 1 has one electron in their outermost shells. Q3 Why isotopes have similar chemical properties Since they have equal number of electrons they have similar chemical properties. Q4 Draw Structure of Calcium Atom Banner 5
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