3 - Covalent and dative covalent bonds Flashcards
What is a covalent bond?
A covalent bond is a shared pair of electrons between two non-metals
What is a dative covalent bond?
A dative covalent bond is when both of the electrons in the shared pair are from a single atom
Example of a dative covalent bond.
Ammonia (NH3) has a lone electron pair that can form a dative bond with a H+ ions to produce an ammonium ion (NH4+).
When a dative bond has formed it is treated as a standard covalent bond.
It reacts in exactly the same way as covalent bonds and does not differ in strength
What is a simple molecular structure?
Covalently bonded molecules held together with weak Van Der Waals forces
What are some examples of simple molecular structures?
- iodine
- ice
- carbon dioxide
- water
- methane
What are the properties of substances with simple molecular structures?
- Low melting and boiling points
- Insoluble (some exceptions)
- Cannot conduct electricity
Why do simple molecular structures have low melting and boiling points?
The Van Der Waals forces between molecules are weak so therefore not a lot of energy is required to overcome the forces
Why are simple molecular structures not soluble?
The molecules are generally non-polar meaning that they cannot interact with water
Why can’t simple molecular structures conduct electricity?
Contains no charged particles
What is a macromolecular structure?
Atoms are held together by covalent bonds with each atom having multiple forming a giant covalent lattice
What are some examples of macromolecular structures?
- diamond
- graphite
- silicon dioxide
- silicon
What are the properties of substances with a macromolecular structure?
- high melting and boiling points
- insoluble
- conductive when solid (graphite)
- rigid and hard (diamond)
Why do macromolecular structures have high melting and boiling points?
There are many strong covalent bonds which require a lot of energy to break
Why is graphite conductive when solid?
- are delocalised electrons between layers
- the electrons can carry a flow of charge and conduct electricity
