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Electron Structure
- ELECTRONS are organised around the nucleus in SHELLS or energy levels, which determine the CHEMICAL PROPERTIES of an atom.
- These shells are filled from the LOWEST to the HIGHEST energy levels, with the INNERMOST shells being filled FIRST.
ELECTRON SHELL RULES
- The FIRST shell can hold up to 2 ELECTRONS.
- The SECOND and THIRD shells can each hold up to 8 ELECTRONS.
ELECTRON CONFIGURATIONS
- Electron configurations can be represented by diagrams or as numbers indicating how many electrons are in each shell.
- For example, the electronic configuration for MAGNESIUM is shown as 2, 8, 2 reflecting its distribution of electrons across the shells (2 in the first shell, 8 in the second and 2 in the third)
- The ATOMIC NUMBER of an element tells you how many protons and, by default, how many ELECTRONS the atom has if it is neutral.
- To determine an element's electronic structure, allocate electrons to the shells according to the rules, starting with the shell closest to the nucleus until you have distributed electrons equal to the atomic number.
Examples of Electronic Structures:
- Using the periodic table, you can see that Chlorine has an atomic number of 17, so Chlorine atoms have 17 ELECTRONS.
- The first shell will be filled with 2 ELECTRONS and the second will be filled with 8 ELECTRONS. There are 7 ELECTRONS left which all go into the THIRD shell.
- This gives the electronic structure for CHLORINE as 2, 8, 7.
Electron Structure
- ELECTRONS are organised around the nucleus in SHELLS or energy levels, which determine the CHEMICAL PROPERTIES of an atom.
- These shells are filled from the LOWEST to the HIGHEST energy levels, with the INNERMOST shells being filled FIRST.
ELECTRON SHELL RULES
- The FIRST shell can hold up to 2 ELECTRONS.
- The SECOND and THIRD shells can each hold up to 8 ELECTRONS.
ELECTRON CONFIGURATIONS
- Electron configurations can be represented by diagrams or as numbers indicating how many electrons are in each shell.
- For example, the electronic configuration for MAGNESIUM is shown as 2, 8, 2 reflecting its distribution of electrons across the shells (2 in the first shell, 8 in the second and 2 in the third)
- The ATOMIC NUMBER of an element tells you how many protons and, by default, how many ELECTRONS the atom has if it is neutral.
- To determine an element's electronic structure, allocate electrons to the shells according to the rules, starting with the shell closest to the nucleus until you have distributed electrons equal to the atomic number.
Examples of Electronic Structures:
- Using the periodic table, you can see that Chlorine has an atomic number of 17, so Chlorine atoms have 17 ELECTRONS.
- The first shell will be filled with 2 ELECTRONS and the second will be filled with 8 ELECTRONS. There are 7 ELECTRONS left which all go into the THIRD shell.
- This gives the electronic structure for CHLORINE as 2, 8, 7.
