Periodic Table Flashcards
Electronegativity
Attraction of atom for e- pair in a covalent bond
Fluorine= most electronegative element
Ionic vs covalent character
↑electroneg differences = ↑ionic character
↑electroneg similarities = ↑ covalent character
Van der Waals forces
Intermolecular forces caused by dipole’s attractions between e-s
Oscillating dipole: dipole continually changes with time
Induced dipole: oscillating dipole induces a neighbouring molecule, etc
Van der waal strength
↑e- no: ↑oscillating and induced dipoles ↑attractive forces between molecules ↑van der waals forces ↑boiling points ↓e- cloud distortion
H bonds and water effect
1/10 strength of covalent bond.
Ice is less dense than water as h bonds hold water molecules apart in an open lattice structure
H bonds
Extra forces above van der waals
Cause higher melting and boiling points
Covalent bond enthalpy
200-500kJ mol-1
H bond enthalpy
5-40
Van der waals enthalpy
~2
Ionic compounds properties
High melting and boiling points
Solid: non-conductive
Melted/dissolved: conductive
Simple molecular structure
Low melting and boiling point
Weak intermolecular forces
Non-conductors
Often soluble and non-polar
Giant covalent structures
Strong forces
High melting and boiling point
Non-conductors
Insoluble
Metal properties
High melting and boiling points
Good thermal and electrical conductivity
Atomic radii trends
Across period: Radii ↓ Nuclear charge ↑ First ionisation energy ↑ ↑boiling point groups 1-4, sharp ↓group 4-5, low group 5-8
Down a group: Extra shells = ↓charge ↓first ionisation energy ↓melting and boiling points
S block reactivity
Most reactive, reactivity ↑down group
Group 2 v reactive with oxygen
