Topic 3 - Covalent Compunds And Seperation Teachniques Flashcards
Why does covalent bonding take place?
So both atoms have a full outer shell so atom is more stable, as it takes more force to break the electrons apart
What are covalent bonds?
Sharing a pair of electrons between non-metal atoms. Each bond consists of a shared pair of electrons, and is very strong.
What does each covalent bond do to an atom?
Each covalent bond provides one extra shared electron for each atom
Each atom has to make enough covalent bonds to fill up its outer shell
What happens if an atom makes covalent bonds with one of more other atoms?
They form a molecule
How is a molecule formed in covalent bonding?
What atoms make covalent bonds with one or more other atoms
Simple molecular covalent substance structure
Only contain a few atoms held together by strong covalent bonds.
Example of a single molecular covalent substance
Carbon dioxide, as the molecules contain only one atom of carbon, which is then bonded with two atoms of oxygen.
Properties of simple molecular covalent substances
Low melting and boiling points - because the weak intermolecular forces break down easily
Non-conductive - substances with simple molecular structure do not conduct electricity as they don’t have any free electrons or an overall electric charge
Other examples of simple covalent molecules
Hydrogen, ammonia, methane and water.
- Have very strong bonds between the atoms, but much weaker forces holding the molecules together
What happens when a simple covalent molecule melts or boils?
The weak ‘intermolecular forces’ break.
Simple molecular substances are gases, liquids or solids with low melting and boiling points.
Do giant molecular covalent substances have charged ions?
NO!
Describe a giant molecular covalent substance
- Contains a lot of non-metal ions, each joined to adjacent atoms by covalent bonds
- Usually arranged in giant regular lattices (very strong structures due to the amount of bonds involved)
How are giant molecular covalent substances structured usually?
In giant regular lattices
Properties of giant molecular covalent substances
- Very high boiling points (because a lot of strong covalent bonds must be broken)
- Variable conductivity (diamonds don’t, but graphite does)
Three examples of very weak intermolecular forces
Hydrogen
Oxygen
Water
Substances with covalent bonds often form molecules what kind of melting and boiling points?
Low melting and boiling points
