Flashcards in Periodicity Deck (22)
What is periodicity?
The regular periodic variation of properties with atomic number and position in the Periodic Table
What is thermal decomposition?
The breaking up of a chemical substance with heat into at least 2 chemical substances
What is a displacement reaction?
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ions
What is disproportionation?
Oxidation and reduction of the same element in a redox reaction
What is the trend in first ionisation energy down a group?
What is the trend in first ionisation energy across a period?
Explain the trend in first ionisation energy down a group
The outer electron is further away from the nucleus and is shielded by electrons in more inner shells so the electrostatic attraction to the nucleus decreases
Explain the trend in first ionisation energy across a period
The number of protons in the nucleus increases and the outer electron is in the same shell, with similar shielding, so electrostatic attraction to the nucleus increases
What are the 2 exceptions to the general trend in first ionisation energy across a period
IE of group 3 is lower than group 2 as the outer electron is in a p-orbital which is higher in energy so evidence for sub-shells
IE of group 6 is lower than group 5 as the outer electron has paired up with another electron in a p-orbital so these repel each other and evidence for spin pairing in atomic orbitals
What do the exceptions in the trend in first ionisation energy across a period support?
The Bohr model of the atom
Give 3 examples of giant covalent lattices
Poor electrical conductivity as no delocalised electrons as all outer shell electrons are used for covalent bonds
Hard as tetrahedral shape allows external forces to be spread throughout lattice
Strong hexagonal layer structure but weak van der Waals' forces between layers
Good electrical conductivity as there are delocalised electrons between layers
Soft as bonding within each layer is strong but weak forces between layers allow layers to slide easily
Essentially a single layer of carbon in the from of graphite
Good electrical conductivity
Outstanding mechanical strength with respect to its thinness
Name 5 points/properties of giant metallic lattices
1) Strong electrostatic attraction between cations and delocalised electrons
2) Can conduct electricity due to delocalised electrons even in solid state
3) High melting and boiling points as attraction strong as high temps are needed to break these bonds
4) Ductile (can be drawn or stretched) and malleable (can be hammered into shape)
5) This is because of delocalised electrons as they can move which allows atoms or layers to slide past each other
Name 6 points/properties about giant covalent lattices
1) Strong covalent bonds between atoms
2) These bonds are throughout the structure
3) High melting and boiling as high temperatures needed to break strong covalent bonds
4) Cannot conduct electricity as no free charged particles except in graphite (and graphene) - electrons are localised
5) Insoluble in both polar and non-polar solvents because covalent bonds are too strong to be broken down by either polar or non-polar solvents
6) Silicon is a metalloid and has a limited number of delocalised electrons that can move through the structure, giving a low conductivity
What type of bonding, structure and forces is present Group 1-3 (except Boron)?
Metallic, giant metallic and strong forces between cations and electrons
What type of bonding, structure and forces is present Group 4?
Covalent, giant covalent and strong forces between atoms
What type of bonding, structure and forces is present Group 5-8?
van der Waals' forces, simple molecular and weak forces between molecules
What happens between groups 1-4?
General increase in melting points as difference in ionic charge increases
What happens between groups 4-5?
Sharp decrease in melting point as from giant structures to simple molecular and strong forces to weak intermolecular forces