2 Bonding 3 Flashcards
Describe the main features of metals in terms of their structure
Positive metal ions arranged in layers with delocalised electrons
Explain why metals can conduct electricity
Delocalised electrons are free to carry charge
Explain why pure metals are soft
Layers of metal ions are free to slide over each other
What is an alloy?
A mixture of two or more elements, at least one of which is a metal
Give a reason for alloying a metal
To make it harder, to make it less reactive
Explain why alloys can be harder than pure metals
Different size of atoms disturb the layers to stop them sliding over each other
What are the three types of chemical bond?
Ionic, covalent and metallic
Which type of bonding involves electrostatic attractions between oppositely charged ions?
Ionic
What is the definition of a covalent bond?
A shared pair of electrons
Why is aluminium a better electrical conductor than sodium?
Aluminium is in group 3, so each atom contributes 3 electrons to the delocalised sea of electrons, leaving behind a 3+ ion. There are more electrons in the sea than sodium, so it is a better conductor.
Why are alloys stronger than pure metals?
There are different sized atoms in the structure which distorts the layers and stops them being able to slide over each other.
Put these bonds in order of strength starting with the weakest: ionic, covalent, metallic
Weakest metallic, then ionic, covalent strongest
How does the charge on the ions produced by the metals in groups 1, 2 and 3 relate to their group number?
It is positive and the same as the group number
How the charge on the ions produced by the non-metals in groups 5, 6 and 7 realte to their group number.
It is equal to the group number minus 8.
Describe the structure of sodium chloride and explain why it has a high boiling point.
It is a 3D lattice of 1+ sodium ions and 1- chloride ions. The electrostatic force between the oppositely charged ions is high, so the bonds are strong. There are many bonds. A lot of energy is needed to overcome the ionic bonds.