Chapter 8 - Covalent Bonding Flashcards
What does the prefix system do?
It tells you what elements make up the compound and in what proportion.
What are the 3 properties of covalent compounds?
1) low melting and boiling point
2) usually soluble in organic solvents but not water.
3) non conductors of electricity.
Explain why covalent compounds have low melting and boiling points in terms of structure and bonding.
They have a simple molecular structure. Only weak van der Waals’ forces of attraction exist between the molecules. Lesser energy is required to overcome the weak van der Waals’ forces of attraction, therefore they have a low melting and boiling point.
Why do covalent compounds not conduct electricity?
They do not have mobile ions or mobile electrons.
Name 3 examples of macromolecules.
Diamond, graphite, sand
Name the 5 properties of diamond.
1) transparent
2) non conductor to electricity
3) hard
4) very high melting and boiling points
5) shiny
In terms of structure and bonding, explain why macromolecules have high boiling and melting points.
Macromolecules have giant molecular structures. Strong covalent bonds exist between atoms. More energy is required to BREAK the strong covalent bonds between atoms, and thus have high melting and boiling points.
What is the structure of a diamond?
Each carbon atom is covalently bonded to four others in a rigid tetrahedral arrangement.
Define allotropes.
Allotropes are different forms of a the same element that differs in physical properties.
Why can graphite conduct electricity?
Within a layer, there are three strong covalent bonds per carbon atom. The fourth outer electron is delocalised. Hence, the presence of delocalised mobile electron ensures that graphite is a good conductor of electricity.
Why can graphite act as a lubricant?
The layers of atoms are only held together by weak van der Waals’ forces. Little energy is required to overcome the weak van der Waals’ forces of attraction. Hence, the layer of carbon atoms can slide over each other easily. Therefore, graphite is soft and slippery, and can act as a lubricant.
How are covalent bonds formed?
Covalent bonds formed when electrons are shared between atoms of non-metals. By sharing the electrons, both atoms get to count the electrons towards noble gas configuration.
Name 3 common properties of macromolecules.
1) high melting&boiling point
2) no electricity conductivity (except graphite)
3) insoluble in both organic solvents and water
Name 3 properties of graphite.
1) soft
2) slippery
3) conducts electricity
Why are some macromolecules hard?
It has a giant molecular structure. The atoms are bonded by strong covalent bonds throughout to form an extensive network structure. Large amount of energy is required to break the strong covalent bonds.
