REVISION NOTES
IGCSE Edexcel Chemistry
1.3 Atomic Structure
1.3.1 Know what is meant by the terms atom and molecule
![edexcel_igcse_chemistry_topic 03 tables_atomic structure_001_atom and molecule definitions](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03-tables_atomic-structure_001_atom-and-molecule-definitions.png)
![edexcel_igcse_chemistry_topic 03_atomic structure_001_ice cream atomic structure analogy](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03_atomic-structure_001_ice-cream-atomic-structure-analogy.png)
1.3.2 Know the structure of an atom in terms of the positions, relative masses and relative charges of subatomic particles
![edexcel_igcse_chemistry_topic 03 tables_atomic structure_002_subatomic particles properties](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03-tables_atomic-structure_002_subatomic-particles-properties.png)
![edexcel_igcse_chemistry_topic 03_atomic structure_002_atomic structure rutherford labelled diagram](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03_atomic-structure_002_atomic-structure-rutherford-labelled-diagram.png)
1.3.3 Know what is meant by the terms atomic number, mass number, isotopes and relative atomic mass (Ar)
![edexcel_igcse_chemistry_topic 03 tables_atomic structure_003_atomic structure key terms](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03-tables_atomic-structure_003_atomic-structure-key-terms.png)
![edexcel_igcse_chemistry_topic 03_atomic structure_003_periodic table key](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-03_atomic-structure_003_periodic-table-key.png)
- Number of protons = atomic number
- Number of electrons =
- For atoms: number of protons = number of electrons (Because atom has overall zero charge)
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- For ions: number of protons ≠ number of electrons
- Number of neutrons = mass number – atomic number
ISOTOPES
- Atoms of same element; same number of protons; different number of neutrons
- They have identical chemical properties, as they have same number of electrons
- Slightly different physical properties
1.3.4 Be able to calculate the relative atomic mass of an element (Ar) from isotopic abundances
ISOTOPIC ABUNDANCE
- Isotopic abundance: percentage of the isotope found in a naturally occurring sample
The relative atomic mass of each element is calculated from the mass number and relative abundances of all the isotopes of a particular element
EXAMPLE
A sample of chlorine gas is a mixture of 2 isotopes, chlorine-35 and chlorine-37. These isotopes occur in specific proportions in the sample i.e. 75% chlorine-35 and 25% chlorine-37. Calculate the relative atomic mass of chlorine in the sample.
![](https://resource.studiaacademy.com/wp-content/uploads/2022/04/1.17.png)
![](https://resource.studiaacademy.com/wp-content/uploads/2022/04/1.171.png)