Covalent bonding
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What is covalent bonding?
A covalent bond is an electrostatic attraction between the shared pair of electrons and the positively charged nuclei of two atoms
Why do simple covalent structures have low boiling points?
They have very low boiling point because the intermolecular forces between the molecules are weak and only need a small amount of energy to overcome.
What are the different types of covalent bonds?
Simple covalent Giant covalent
How are covalent bonds represented?
A line between the atoms e.g. h-h
Why are covalent bonds formed?
To complete an outer shell
Why when Hydrogen bonds is Hydrogen not helium?
Because the identity of an element is based on the number of protons.
Why do bonds make the ions more stable?
When a chemical reaction takes place, energy is released leaving the product with less energy making it more stable.
What is the relation of a paired share of electrons to another (in terms of positioning)
The shared electrons move as far away as possible, because electrons repel each other
Can water be bent?
Water can be bent Slightly polar ends electrical charged object to water -> bend
how are double covalent bonds represented?
two lines
draw dot and cross diagrams
How are covalent structures held together between molecules?
Weak intermolecular forces
Trend between melting and boiling point of halogens
down the group higher melting and boiling points
Do covalent ions conduct electricity
no except graphene or graphite
Do covalent structures dissolve in water?
Covalent structures usually do not dissolve in water.
arrangement in diamond
tetrahedral arrangement, giant covalent
Graphite structure
Graphite’s structure is a bit like a layer structure, but still giant covalent structure with layers in between. Carbon is bonded to three carbons and a delocalised electron
structure of C60 fullerene
C60 fullerene is a simple covalent structure with a delocalised electron per carbon atom, but they cannot move between molecules.
Trend between M(small r) and intermolecular forces
Usually intermolecular forces are stronger when there is a higher relative molecular mass but not always.
Graphite’s structure
Layers with 3 shared electrons and delocalised electrons which means graphite can conduct electricity. There are weak intermolecular forces between the layers making graphite soft.
Why is melting point of diamond high(around 4000 degrees celcius)?
Diamond has a very high melting point. This is because diamond is in a giant covalent structure (or macro molecular covalent). This means that there are millions of strong covalent bonds between the carbon atoms. This is a strong structure and is hard to break. This means that a lot of energy is needed to break all the bonds.
Why does Fullerene have a low melting and boiling point?
Fullerene has a low melting point. This is because fullerene is in a simple molecular structure and there are weak intermolecular bonds between the atoms. This means that little energy is needed to overcome these bonds.
Explain why simple covalent molecules have: 1) Low melting points 2) Cannot conduct electricity
Simple covalent molecules cannot conduct electricity as there are no delocalised electrons or oppositely charged ions. Simple covalent molecules have a low melting point because they have weak intermolecular forces. These forces are weak and easy to overcome.
Explain why: Giant covalent structures have high melting/boiling points?
• Giant covalent structures have a high boiling point • This is because giant covalent have a giant covalent structure • This means that there are many covalent bonds • These bonds are strong and hard to break requiring a lot of thermal energy to break them