Covalent Compounds Between Non - Metal Atoms Flashcards
What do some covalently bonded substances consist of?
Simple molecules such as H2, O2, HCl, NH3
When do covalent bonds form?
When atoms share pairs of electrons, these bonds between atoms are very strong
What does O2 have?
A double bond
What have low melting points and boiling points ?
Substances made of simple molecules - gases , liquids and solids that are easy to melt
What are the forces between molecules?
Weak. It is these weak intermolecular forces that are broken when the substance melts or boils, not the strong covalent bonds
Why don’t substances that consist of simple molecules conduct electricity
Because the molecules do not have an overall electrical charge
When are giant covalent structure formed?
When huge numbers of atoms are held together by a network of covalent bonds
What are 2 giant covalent structures?
Diamond and silicon, all the atoms are linked by strong covalent bond so they have very high melting points
In diamond what does each carbon atom form?
Four covalent bonds with other Carbon atoms in a giant covalent structure so diamond is very hard
Why don’t most giant covalent structures conduct electricity
They do not have any charged particles that can move
Why is graphite (another giant covalent structure of carbon) unusual
It conducts electricity and is quite soft
What happens in graphite?
Each carbon atom bonds to three others, forming layers . The layers can slide over each other because there are no covalent bonds between the layers, so graphite is quite soft and slippery
What are the forces between the layers in graphite
Weak intermolecular forces. One electron from each carbon atom is delocalised - these delocalised electrons allow graphite to conduct heat and electricity
What can Carbon also form?
Fullerenes with different numbers if carbon atoms these are made of hexagonal rings of carbon atoms
What can fullerenes be used for?
Drug delivery into the body, in lubricants, as catalysts and in nanotubes for reinforcing materials (eg tennis rackets)
