2D Flashcards
Metallic bonding
Electrostatic attraction between positive metal ions and negative delocalised electrons
What are delocalised electrons
Metals have a relatively low 1st ionisation energy, the valence electrons are held loosely and in a metallic lattice, each atom loses its valence electron/s which then extend through the lattice occupying a new set of energy levels. These are said to be delocalised
Ionic bonding
electrostatic attraction between the positive cations and negative anions
covalent bonding
Electrostatic attraction between the shared pair of electrons and the nuclei of the bonded atoms
Intermolecular bonding
Electrostatic attraction between dipoles on molecules
How many bonds can Group 1/ Group 7 make
1
How many bonds can Group 6 make
double bond
How many bonds can Group 5 make
Triple bonding
Octet rule
When an atom of an element has 8 electrons in its outer shell i is said to have an octet
When does the octet rule not work?
- Atoms in elements tat are in Group 3 or higher - have access to 3d subshell which holds 10 electrons
- unpaired electrons can pair up - max number of electron pairs in an outer shell is number of electrons in outer shell
What is a dative covalent bond?
A covalent bond where both of the electrons come from a single bond
Eg : in an ammonium ion where in ammonia, Nitrogen has 2 free electrons that can form a bond with a hydrogen ion with no electrons
What is needed for a dative covalent bond to form
- The acceptor atom must be electron deficient - available orbitals for electrons to occupy
In what way is a dative and covalent bond the same
- Dative and Covalent bonds are exactly the same
- Same length
- Same average bond enthalpy
What is a lone pair
A pair or electrons not used in bonding on the outer shell
What is a Polyatomic ion
A group of atoms with a charge - For example a carbonate ion
What is a giant ionic lattice
A regular 3D of oppositely charged ions, held together by electrostatic attractions
Features of a giant ionic lattice
- Conducts electricity when molten or aqueous - not solid
- High MP, BP
- Ionic bonding
Giant metallic lattice
A regular 3D arrangement of positive ions and delocalised electrons
Features of Giant metallic lattice
- High MP and BP
- Conducts electricity when solid or liquid
- Metallic bonding
Giant covalent lattice
A 3D structure of atoms that share electrons with each other
Features of Giant Covalent lattice
- High MP/BP
- doesn’t conduct electricity when solid or liquid
- Covalent bonding
Simple Covalent molecule
- 3D structure of molecules held together by weak intermolecular forces
Features of A simple covalent molecule
- Low MP/BP
- Cannot conduct electricity solid or molten
Why can’t simple covalent molecules conduct electricity
Negative ions or electrons are no free to move and act as mobile charge carriers as they are fixed in place and can’t carry charge through the structure.
What is a Simple covalent molecule
Small units containing a definite number of atoms with a definite molecular formula.
What is a Giant covalent molecule
Billions of atoms held together to form a network of strong covalent bonds
Structure of Graphite
- Parallel layers of hexagonally arranged carbon atoms.
- Layers bonded by weak London forces
Features of Graphite
- Can conduct electricity as only 3 of Carbons 4 valence electrons so has free delocalised electrons that can move and carry charge
- Soft as weak London Forces between layers easily broken and layers slide over each others
What is Graphene
A single sheet of graphite structure, similar conductivity and strength properties
Structure and Features of Diamond
- Tetrahedral structure, all 4 valence electrons used so cannot conduct electricity as no delocalised electrons.
- Hard as tetrahedral structure of each carbon atom spreads forces through structure and strong covalent bonds need lots of energy to break.
Why do metals have a high MP and BP
Due to strong electrostatic attraction between pos metal ions and neg electron
Why are Metals better conductors when molten
Both delocalised electrons and positive ions can move and act as mobile charge carriers through the structure
Why do MP across period 3 increase
- Metal atoms donate their valence electrons to electron sea
- As you go across period valence electrons increase in delocalised electron sea - stronger electrostatic attractions between metal ions and delocalised electrons
What does malleable mean?
Easily bent into different shape
What does ductile mean
Can be stretched into a wire
Why are metals both malleable and ductile?
Layers of ions easily slide over each other
What is an alloy, why do alloys have different properties?
Different metal mixtures - metal ions have different sizes so layers cannot slide over each other as easily.
What alloy is brass made out of
Copper and Zinc
What metals is stainless steel alloy made of?
Iron and Chromium
What shape and bond angle does a molecule with 2BP and 0LP have?
Linear shape - bond angle of 180
What shape and bond angle does a molecule with 3BP and 0LP have?
Trigonal Planar - bond angle of 120 degrees
What shape and bond angle does a molecule with 4BP and 0LP have?
Tetrahedral - bond angle of 109.5 degrees
What shape and bond angle does a molecule with 5BP and 0LP have?
Trigonal bipyramidal, bond angles of 90 and 120 degrees
Wha shape and bond angle does a molecule with 6BP and 0LP have?
Octahedral - bond angle of 90 degrees
What shape and bond angle does a molecule with 2BP and 2LP have?
Non linear shape, bond angle of 104.5
What shape and bond angle does a molecule of 3BP and 1LP have?
Pyramidal shape - bond angle of 107 degrees
Why is a double bond considered a single bond when regarding shapes?
It is in one region of electron density
What is electronegativity
The measure of attraction of a bonded atom for the pair of electrons in a covalent bond
