Electronic structure
- Created by: Rachh
- Created on: 25-12-12 16:49
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- Electronic structure
- Electron shells
- Electrons have fixed energies.
- Electrons move around the nucleus in shells, or energy levels.
- The shells are divided up into sub-shells as the electrons within a shell have different energies.
- The s- sub-shell has 1 orbital so 2 electrons.
- The p sub-shell has 3 orbitals so 6 electrons.
- The d sub-shell has 5 orbitals so 10 electrons.
- The f sub-shell has 7 orbitals so 14 electrons.
- Showing electron configurations
- Sub-shell notation is a way of writing out the configuration of electrons.
- eg an atom of Neon would be written as 1s2 2s2 2p6
- Another way to show it is by drawing arrows in boxes.
- The up and down arrows represent the electrons spinning in different directions.
- Two electrons can only occupy the same orbital if they have opposite spin.
- The up and down arrows represent the electrons spinning in different directions.
- Energy level diagrams are also used.
- They also show the energy of the electrons in different orbitals.
- These show the number of electrons and their arrangement.
- Sub-shell notation is a way of writing out the configuration of electrons.
- Working out electron configurations
- Electrons fill up the lowest energy sub-shells first.
- Electrons fill orbitals singly before they start sharing.
- For the configuration of ions from the s and p blocks of the periodic table, add or remove electrons to or from the highest energy occupied sub-shell.
- eg Mg = 1s2 2s2 2p6 3s2 and Mg2+ = 1s2 2s2 2p6
- Nobe gas symbols in square brackets are sometimes used in electron configurations.
- eg calcium (1s2 2s2 2p6 3s2 3p6 4s2) can be shortened to [Ar] 4s2
- Transition metals:
- Odd ones out:
- Copper (Cu): 1s2 2s2 2p6 3s2 3p6 4s1 3d10
- Chromium (Cr): 1s2 2s2 2p6 3s2 3p6 4s1 3d5
- When transition metals become ions, they lose their 4s electrons before their 3d electrons.
- eg. Fe: 1s2 2s2 2p6 3s2 3p6 4s2 3d6 and Fe3+: 1s2 2s2 2p6 3s2 3p6 3d5
- Odd ones out:
- Electronic structure and chemical properties
- The s-block elements (group 1 and 2) easily lose their outer electrons to form positive ions with an inert gas configuration.
- The elements in groups 5,6, and 7 (p block) can gain 1,2 or 3 electrons to form negative ions with an inert gas configuration.
- Group 0 (the inert gases) have completely filled s and p sub-shells.
- Electron shells
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