Module 2.2: Electrons, bonding and structure

ORBITALS -

• Orbital: A region of space in an atom where electrons may be found.
• Each orbital can hold up to 2 electrons - they don't repel each other as they have opposite spins.
• S-orbital: Spherical shape. Each shell contains one s-orbital, so can have up to 2 s-electrons.
• P-orbital: Dumb-bell shape. From the second shell, each shell contains 3 p-orbitals, so each shell can have up to 6 p-electrons.
• D-orbital: From third shell, each shell contains 5 d-orbitals = up to 10 d-electrons.
• F-orbital: From fourth shell, each shell contains 7 f-orbitals = up to 14 f-electrons.

FILLING SUB-SHELLS -

• Electrons are added to shells one at a time.
• The lowest available energy level is filled first.
• Each energy level must be full before the next energy level begins to fill.
• Each orbital in a sub-shell is filled singly before pairing starts.

IONIC BONDING -

• Definition: The strong electrostatic force of attraction beween oppositely-charged ions.
• Electrons are transferred from the metal atom to the non-metal atom, forming oppositely-charged ions. These are bonded together by electrostatic attraction.
• Giant ionic lattice: Each ion is surrounded by oppositely charged ions. The ions attract each other from all directions.
• Ionic compounds have high melting and boiling points - lots of energy is needed to break the strong electrostatic bonds holding the ions together. The greater the charge on the ions, the stronger the electrostatic forces are between the ions.
• When solid: Do not conduct electricity - ions are in fixed positions and cannot move.
• When melted/dissolved in water: Conduct electricity - lattice breaks down and ions are free to move and conduct electricity.
• Solubility: Dissolve in polar solvents. Polar molecules e.g. water break down the lattice by surrounding each ion, forming a solution. The slight charges on the polar substance attract the charged ions in the giant ionic lattice = lattice disrupted, ions pulled out of it.

COVALENT BONDING -

• Definition: The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
• This attraction overcomes…