Bonding: Part 1 Flashcards
Types of chemical bonds:
Ionic, covalent and metallic
What is ionic bonding?
Electrostatic attraction between oppositely charged ions. Electron transfer from metal + ions and non-metal - ions
What is covalent bonding?
The sharing of a pair of electrons, causing strong electrostatic attraction between a shared pair and the nucleis. Non-metal compounds
What is metallic bonding?
The strong electrostatic attraction of a lattice of positive metal ions to a sea of delocalised electrons. Occurs in metals
Key definitions of each bonding
-ionic = the electrostatic attraction between positive and negative ions
-covalent = strong electrostatic attraction between a shared pair of electrons and the nuclei on the bonded atoms
-Metallic =
What are crystal structures?
Crystals are solids where the particles have a regular arrangement and are held together by forces of attraction which could be intramolecular forces or weaker intermolecular forces. The strength of the attractive forces impact properties e.g. melting points
Types of crystal structures:
Ionic, metallic, simple covalent and giant covalent
Ionic crystals
Strong electrostatic attractions between ions and positive charges -> typically high melting points as the bonds spread throughout the molecule and require lots of energy to break
Metallic crystals
A lattice of positive ions surrounded by a sea of delocalised electrons -> high melting points due to strong attraction between ions and electrons
Simple covalent crystals
Consist of a regular array of molecules. Covalent bonds hold atoms together within each molecule but intermolecular forces hold each molecule to the next forming the crystal structure. When heated, as it melts only the weak intermolecular forces remain (covalent bonds remain) -> low melting points
Giant covalent crystals
Small molecules with weak intermolecular forces, some covalent substances are macromolecular and the covalent bonds extend throughout the entire structure. Because all bonds in a macromolecular crystal are covalent -> high melting points due to strength of bonds
Macromolecular crystal examples
Diamond and graphite -> allotropes, entirely carbon but different structural forms
Diamonds info
-4 strong covalent bonds
-Tetrahedral arrangement, 3D strong structure
-Hard material because of the bonds
-Very high melting point
-Doesn’t conduct electricity = no delocalised electrons to move and carry and charge
Graphite info
-Layer of carbon each forming 3 bonds
4th valence electron, no bond forms from it so delocalised between layers
-Mean separate layers are held together by London forces -> unusual properties
-Fairly soft so each layer can slide over each other
-Conducts electricity because the delocalised electron
-High melting point -> lots of covalent bonds still need to be broken
Buckminsterfullerene info
-Spherical cage made up of 60 carbon atoms
-Carbon nanotubes = whatever length needed, strong and light
-can conduct electricity = many applications in electrical devices
Melting and boiling points of giant ionic compounds
Strong electrostatic attraction in 3 dimensions requiring lots of energy to break these bonds. All solid at room temp. Greater ionic charge = higher melting and boiling points
Electrical conductivity of giant ionic compounds
Electricity is a flow of charged particles, solid giant compounds don’t conduct because they are held in fixed positions despite the charged ions. When molten they do conduct as ion as are now mobile
Solubility of giant ionic compounds
Dissolve in polar solvents, like water because these molecules can break down the lattice and surround each ion. Larger the charge = harder to break down in polar solvents
-Solubility requires: A broken down ionic lattice and water molecules that attract surrounding molecules
What causes a giant ionic lattice?
Results from regular arrangements of oppositely charged ions strongly attracted in all directions
What are lone pairs?
Pairs of electrons in the outer shell of an atom not involved in covalent bonds
