Electron Structure

Electron Structure

1. Energy levels/ Quantum shells

   • Principle Quantum number
     • Describes the position of the shell in the atom.
     • The larger the principle quantum number is the further away it is from the nucleus,
     • 1n
       • Energy level - 1
       • Maximum number of electrons - 2
     • 2n
       • Energy level - 2
       • Maximum number of electrons - 8
     • 3n
       • Energy level - 3
       • Maximum number of electrons- 18
     • 4n
       • Energy level - 4
       • Maximum number of electrons - 32

2. Orbitals and Subshells

   • S-Subshell
     • Spherical shape
     • Has just 1 orbital
       • Holds up to 2 electrons
   • P-Subshell
     • Consists of 3 orbitals
       • Orbitals are dumbbell shaped
     • Holds up to 6 electrons
   • D-Subshell
     • Consists of 5 orbitals
     • Complex shape
     • Holds up to 10 electrons
   • F-Orbitals
     • Complex shape
     • Consists of 7 orbitals
     • Holds up to 14 electrons
   • Definition: An atomic orbital is the volume of space within an atom that can hold up to 2 electrons with opposite spins
     • Key definition: A covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atom
       • Key definition: A dative bond is a bond where the shared pair of electrons has been donated by the same atom
         • The ammonium ion contains a dative bond
         • The oxonium ion contains a dative bond
         • Definition: A simple covalent lattice is a 3-d structure of molecules bonded together by weak IMF
           • Definition: A giant Covalent lattice is a 3d lattice structure of atoms bonded together by strong covalent bonds

3. Periodic table

   • Arranged based on the reactivity and properties of elements
     • Reactivity is dependent on outer shell electrons
   • Can be divided into blocks depending on which subshell contains the outermost electron
     • Group 1 and 2 are the S-block
     • The transition metals are the D-block
     • Group 3 to 0 are the P-block

4. Box diagrams

   • As orbitals have varying shapes they are often represented as boxes
   • Each box can hold up to 2 electrons which are represented as arrows
     • ^ l l v
       • ^ l
         • ^ l
   • 1) Electrons should be added one at a time 2) the lowest available energy level is to be filled first 3) Each energy level must be filled before the higher energy level is filled 4)When a subtle is filled up with electrons each orbital is filled singularly before pairing starts 5) An orbital can hold up to 2 electrons, each with opposite spins.

5. Electron configurations

   • s
     • 1
       • Number of electrons in subshell
     • 1
       • Principle Quantum Number
     • Sub-shell type

6. Bonding

   • Metallic
     • positively charged ions held together by a sea of delocalised electrons
     • Properties
       • Conducts electricity
         • delocalised electrons free to move and carry the charge
       • Insoluble in water
         • No interactions with water molecules
       • Variable melting and boiling points
         • the more positive the ion the more it attracts the electrons the higher the melting point
   • Covalent
     • Simple molecular structures
       • Molecules held together by weak IMF
       • Atoms bonded by strong covalent bonds
       • Properties
         • Low melting and boiling points
           • Weak IMFS need little energy to overcome
         • Not conductors of electricity
         • Soluble only in non polar substances
           • Forces between solvent and covalent molecule weaken lattice and it dissolves
     • Macromolecules
       • Millions of atoms bonded by millions of strong covalent bods
       • Properties
         • High melting and boiling point
           • Strong covalent bonds need a lot of energy to overcome
         • Non-soluble
           • No interaction between water molecules
         • Conductivity?
           • Only graphite (delocalised e- move through and carry the charge)
   • Ionic
     • Definition: Ionic bonding is the electrostatic force of attraction between positive and negative ions
     • Takes place between metals and non-metals
       • Metal forms a positive ion by losing electrons
         • Cations
       • Non-metal forms a negative ion by gaining electrons
         • Anions
       • Attraction between ions depends on, Charge and Size
         • The larger the charge the larger the force of attraction
         • The smaller the atom the larger the force of attraction
     • • In exam only the 2nd half of this diagram is needed
       • Metal ion should always have an empty outer shell (this isn't shown on this diagram)
     • Structure
       • Ionic compounds form Giant ionic lattices
       • • Each Cl ion is surrounded by 6 Na ions and vice versa
           • 6:6 Cordination
         • Each ion is attracted by the oppositely charged ions surrounding it
           • • Only draw the outer shell
             • Only the final diagram needs to be drawn in an exam
             • Double and triple covalent bonds are also possible
     • Properties
       • High melting and boiling points
         • Solid at RT
         • Large amounts of energy are required to overcome the strong electrostatic forces between ions
       • Conducts electricity IN SOLUTION
         • When solid ions are in fixed positions and can't move through the structure therefore cannot carry the charge
           • When in solution the lattice has been broken down so the ions are free to move and carry the current
       • Soluble in water
         • Polar water molecules break down lattice by surrounding each ion by water molecules forming a solution

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