Topic 2 - Bonding Flashcards
Definition if ionic bonding
A strong electrostatic force of attraction between oppositely charged ions in a lattice
Why do chemical bonds form?
When atoms share or transfer electrons to achieve a more stable electron arrangement, often a full outer main level of electrons.
Formula of sulfate
SO4 (2-)
Formula of nitrate
NO3 (-)
Formula of Hydroxide
OH (-)
Formula of carbonate
CO3 (2-)
Formula of Ammonium
NH4 (+)
Properties of ionically bonded compounds …
Always solid at room temp
Giant structures = high melting points
Only conducts when molten or in aqueous solution as ions are not free when solid
Definition of metallic bonding
Strong electrostatic force of attraction between positive metal ions and sea of delocalised electrons
Structure in metallic bonding
Giant metallic lattice
Properties of metals x4
Good conductors of electricity as delocalised electrons can move throughout the structure.
High thermal conductivity due to delocalised electrons and the closely packed ions allowing vigorous vibrations.
Malleable and Ductile - arranged in layers which can slide and each metal ion will still be in the same environment.
High melting points
What does the strength of a metal depend on?
Charge on the ion - bigger charge = more delocalised electrons and the strong the force of attraction between electrons and metal ions.
Size of the ion - Smaller ion means the closer the electrons are to the positive nucleus = stronger bond
What is a covalent bond?
A strong electrostatic force of attraction between positive nuclei of the atoms involved and the shared pair of electrons
What’s the difference between a single covalent bond and multiple covalent bonds?
A single covalent bond contains one pair of shared electrons
Multiple covalent bonds contain multiple shared pairs
What is a dative covalent bond?
A co-ordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom.
Melting and boiling of ionic structure
High as lots of energy is required to overcome the strong electrostatic forces of attraction between oppositely charged ions.
Other word for giant covalent
Macromolecular
Diamond structure and properties x4
Each carbon strongly, covalently bonded to 4 other carbons in a giant lattice of atoms which are arranged tetrahedrally.
High melting and boiling
Does not conduct electricity as there are no freely moving charged particles
Very hard as strong covalent bonds hold atoms in fixed positions
Graphite structure and properties?
Each carbon atom strongly, covalently bonded to 3 others forming a giant lattice of atoms in a trigonal planar arrangement.
High melting and boiling point
Does conduct electricity as between layers there are delocalised electrons that can move freely and conduct - can only conduct electricity along hexagonal planes and not vertically throughout the structure.
Soft and slippery as there are weak forces of attraction (VDW forces) between the layers which are easily overcome to allow the layers to slide relative to one another
Temperature of any substance is ….
Directly proportional to the mean kinetic energy of the particles
Why do liquids cool as they evaporate?
As some of the KE is used to overcome the forces of attraction between particles to allow them to escape.
The leads to a lower mean KE and therefore a lower T
What happens when a solid is heated?
Particles vibrate faster
KE + T increase
What happens during melting?
Heat energy is used to overcome or partially overcome the forces of attraction between particles instead of increasing the KE. Therefore T is constant through melting.
As KE remains constant
What happens during boiling.
Heat energy is used to overcome the forces or bonds between the particles rather than increase the KE.
Liquid boils but KE remains constant so T remains constant