7.3 Periodic Trends In Bonding And Structure
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What are the metalloids?
Boron Silicon Germanium Arsenic Antimony
Which metal is liquid at room temperature?
Mercury
One constant property of all metals
They can conduct electricity
Describe metallic bonding
Each atom donates negative outer shell electrons, which form a sea of delocalised electrons Positive ions - cations - are left behind It is the strong electrostatic force of attraction between the cations and delocalised electrons
What maintains the structure of metals?
The cations, which are fixed in position
What is a giant metallic lattice?
A 3D structure of positive ions and delocalised electrons, bonded together by strong metallic bonds
Properties of metals
Strong metallic bonds High electrical conductivity High melting and boiling points
Why can metals conduct electricity?
The delocalised electrons are free to move This carries charge across a structure
Why do most metals have high melting and boiling points?
The strength of the metallic ones cause the high melting and boiling points A large amount of energy is required to overcome the strong electrostatic forces of attraction between cations and electrons
Solubility of metals
Metals do not dissolve - any interactions with polar water cause reactions, not dissolving
Forces between simple molecular substances?
Weak intermolecular forces
MP/BPs of simple molecular structures
Low, as the intermolecular forces holding the molecules together are weak, so little energy is required to overcome them
Which non metals form a giant covalent lattice?
Carbon Silicon Boron
What is a giant covalent lattice?
A 3D structure of atoms, bonded together by strong covalent bonds
Structure of Carbon atoms in diamond
Tetrahedral arrangement Bond angle of 109.5 Each Carbon forms bonds with 4 other Carbon atoms
MP/BPs of giant covalent lattices
Very high MP/BPs Covalent bonds are strong High temperatures are required to overcome these strong bonds
Solubility of giant covalent lattices
Insoluble in almost all solvents Covalent bonds holding atoms together are too strong to be broken by interaction with solvents
Can giant covalent lattices conduct electricity?
No, except graphene and graphite
Why can diamond and silicon not conduct electricity?
All four outer electrons are covalent bonded No free electrons are available to move and carry electricity
Bond angle in graphene and graphite
120
What happens to MP from groups 1-3?
It increases Cations have higher charges More delocalised electrons - lost from the outer shells Stronger electrostatic force of attraction - higher MP
Why is there a sharp decrease in melting point between group 14 and 15?
There is a change from giant to simple molecular structures