7.3 - Periodic trends in bonding and structure Flashcards
(8 cards)
What structure do all metals have?
A giant metallic lattice structure
Describe the cations and delocalised electrons in giant metallic lattice structures
- Cations are in fixed positions
- Delocalised electrons are free mobile charge carriers
Describe the properties of metals
- High electrical conductivity: delocalised electrons act as free mobile charge carriers enabling metals to conduct electricity
- High melting and boiling point: high bond enthalpy of metallic bonds, delocalised electrons have a strong attraction to cations
- Do not dissolve: any interactions would lead to a reaction rather than dissolving
Give two examples of giant covalent lattices and state the bond angle
Carbon(diamond) and silicon, tetrahedral - 109.5°
Describe the properties of giant covalent lattices
- Non-conductors of electricity: all 4 outer electrons are involved in covalent bonding and no mobile charge carriers
- HOWEVER, in graphite and graphene, only 3 electrons are involved in covalent bonds so one electron from each atom acts as a mobile charge carrier, conducting electricity - High melting and boiling points: high bond enthalpy of covalent bonds
- Do not dissolve: covalent bonds are too strong to be broken by interaction with solvents
What is the structure of the elements in period 2?
Giant metallic lattice structure: Li, Be
Giant covalent structure: B, C
Simple molecular structure: N₂, O₂, F₂, Ne
What is the structure of the elements in period 3?
Giant metallic lattice structure: Na, Mg, Al
Giant covalent structure: Si
Simple molecular structure: P₄, S₈, Cl₂, Ar
Summary:
Giant metallic lattice structure: strong metallic bonds between cations and delocalised electrons
Giant covalent structure: strong covalent bonds between atoms
Simple molecular structure: Weak London forces between molecules
