This page contains the detailed and easy notes for Edexcel IGCSE Chemistry Atomic Structure for revision and understanding Atomic Structure.

Edexcel IGCSE Paper 1: Complete Revision Summary

Atomic Structure.

• 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

• 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

• 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 (1)

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Structure of Atoms

No. of Proton, Neutron and Electron

• 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

For Example

Sodium = No. of electron =2,8,1

Magnesium = 2,8,2

1. All Elements React to gain full outer shell
2. The number of electron in the outermost shell is the group number of the elements
3. Elements in the same group have same number of electron in their outer most shell

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

0^2- -2 charged as it has gained two electrons

Isotopes

1. a) Members of the same elements
2. b) Have same atomic number but different mass number
3. c) Same number of electron and protons but different neutrons
4. d) Since electron numbers are the same they show similar chemical properties
5. 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

DISCLAIMER

Disclaimer: I have tried by level best to provide the answers and video explanations to the best of my knowledge. All the answers and notes are written by me and if there is any similarity in the content then it is purely coincidental. But this is not an alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

BBC Bitesize

Edexcel IGCSE Science book

Wikipedia

Wikimedia Commons

Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

Atomic Structure

• A Simple Atomic Model 1 MS
• A Simple Atomic Model 1 QP
• A Simple Atomic Model 2 MS
• A Simple Atomic Model 2 QP
• A Simple Atomic Model 3 MS
• A Simple Atomic Model 3 QP