1.3 Bonding
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What is significant about noble gases?
They have full outer shells Therefore are unreactive so don’t form compounds
What do we use to show transfer of electrons?
Dot and cross diagrams
What do you do when an ion is formed?
Put square brackets around the diagram and put the relative charge on the outside
What does ionic bonding consist of?
A non-metal and a metal forming ions by transfer of electrons
How are ions formed?
When atoms gain or lose electron in order to obtain a full outer shell (or noble gas configuration)
What is an ionic bond?
A strong electrostatic force of attraction between oppositely charged ions
What is the boiling/melting point of ionic bonding? Why?
High Boiling/Melting Point The strong electrostatic force of attraction between the oppositely charged ions require a great deal of heat energy to overcome
What are some properties of ionic compounds?
High melting/boiling point Brittle No current can flow and cannot conduct electricity unless molten or in a solution If moved the charges repel each other
Why can ionic substances only conduct when in a solution or molten?
The ions need to be delocalised so they are free to move
What is covalent bonding?
A bond formed between a non-metal and a non-metal consisting of shared pairs of electrons from the outer shells of each atom
What is a covalent bond?
An electrostatic force of attraction between the positively charged nucleus and the negatively charged electrons in the bonding pair
What is a co-ordinate bond?
A covalent bond where both the electrons in the bonding pair come from one atom Symbol: →
What is significant about co-ordinate bonds?
After formation they become indistinguishable therefore they are just the same as normal covalent bonds
Give an example of a co-ordinate bond?
(In square brackets with a positive charge on the outside) H | H - N → H | H Ammonium where in the co-ordinate bond both electrons came from the nitrogen
What are the features of diamond?
Covalent bonding - each carbon joined to 4 other carbons Creating a giant lattice Macromolecular structure Very high melting point Strong hard substance Doesn’t conduct electricity
Why does diamond and graphite have a very high melting point?
There are lots of strong covalent bonds therefore a lot of energy is required to break them
Why is diamond very strong? What is it’s Mohs?
Because each carbon is bonded to 4 other carbons 10 Mohs (mineral hardness scale)
What are the features of graphite?
Covalent bonding - each carbon is joined by three other carbons Macromolecular structure Very high melting point Soft and slippery Conducts electricity
Why is graphite soft and slippery? What is it’s Mohs?
Because it has a layered structure so the sheets can move over each other as they have comparatively weaker van der waal forces between these layers 1-2 Mohs (mineral hardness scale)
Why can graphite conduct electricity?
As there are only 3 carbons bonded to each carbon there are delocalised electrons (one from each carbon) that can move within the layers and allow current to flow
What are diamond and graphite?
Allotropes They both have the same element just arranged in a different structure
What are some features of silicon dioxide?
Covalent bonding Macromolecular structure High melting point (not as high as diamond or graphite) Strong hard substance Doesn’t conduct electricity
What is significant about iodine?
It is a molecular crystal
What are some features of iodine?
Solid at room temperature Molecular crystal = regular structure Low melting/boiling point Doesn’t conduct electricity Sublimes when heated gently (solid to gas) Non-polar