AS.5 Bonding Flashcards
Metallic bonds
electrostatic attraction between positively charged ions and a sea of delocalised electrons
diagram to represent metallic bonds
cations relative charge in a circle
sea of delocalised electrons represented by appropriate number of minuses
giant
continous bonds
lattice
regular and repeating pattern
giant metallic lattice - melting and boiling point
very high
strong metallic bonds throughout structure
giant metallic lattice - electrical conductivity
very high
delocalised electrons are free to move and carry charge
giant metallic lattice - solubility
insoluble
some may react with water
comparing the strength of metallic bonds
more e- and higher nucleur charge
stronger electrostatic attraction
stronger metallic bond
higher melting/boiling point
ionic bonds
electrostatic attraction between two oppositely charged ions
dot and cross ionic
square brackets with charge in top right corner
no dots or crosses on metal
appropriate dots and crosses on non-metal
number in front to indicate how many
why do metals and non metals lose/gain electrons
full outer shell- more stable
giant ionic lattice - melting and boiling point
high
strong ionic bonds throughout
giant ionic lattice - electrical conductivity
solids do not conduct - ions are in fixed position - not mobile
molten/aqueous do conduct - ions are free to move
Covalent bond
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the 2 bonded atoms
Dative covalent bonds
Both electrons in the covalent bond come from one of the atoms
The atom giving the electron pair must have a lone pair
The atom accepting the lone pair must have empty orbital space
Why do molecules have a specific 3D shape
Result in minimum amount of repulsion between electron pairs
Repulsion
MOST
Lone pair to lone pair
Lone pair to bond pair
Bond pair to bond pair
LEAST
Linear
2-0-2
180*
Trigonal planar
3-0-3
120*
Tetrahedral
4-0-4
109.5*
Pyramidal
3-1-4
107*
Non-linear
2-2-4
104.5*
Lone pairs repel bonding pairs
Octahedral
6-0-6
90*
Each lone pair decreases angle by…
2.5*
Electronegativity
Ability of an atom to attract the electron pair in a covalent bond
Electronegativity increases as…..
Atomic radius decreases
Bonding pair is closer to nucleus
Polar molecules
Imbalanced electronegativity
Has polar bonds
Asymmetrical
Intermolecular forces
Bonds between molecules in a simple covalent lattice
London forces
Non-polar molecule
Uneven distribution of electrons
Creates temporary dipole
Induces dipole in neighbouring molecule
Two dipoles attract each other
London force strength
1) no of electrons
2) surface area contact points
Permanent dipole dipole forces
Polar molecules
Dipoles attract each other
Stronger than London forces because permanent
Hydrogen bonds
H-F
H-O
H-N
Strongest IMF
Very polar
Lone pair on F/O/N is very attracted to H
Why ice is less dense than water
Each water molecule is able to form 4 hydrogen bonds as molecules are far more ordered in solid state
Increase in number of hydrogen bonds that can be formed pushes molecules further apart
Now adopt tetrahedral shape
Simple molecular lattice - melting and boiling point
Low
Breaking IMF which are much weaker than bonds
Simple molecular lattice - electrical conductivity
Very low
No mobile electrons or ions
Simple molecular lattice - solubility
Polar dissolves in polar solvent
Non polar dissolves in non polar solvent
Giant covalent lattice vs simple covalent lattice
Giant has covalent bonds spread throughout so breaking bonds instead of IMF
Graphite
Each carbon forms 3 covalent bonds
Trigonal planar
Hexagonal layers
1 delocalised electron between layers - London forces
Diamond
Each carbon has 4 covalent bonds
Tetrahedral
SO2 has same structure
Giant covalent lattice - melting and boiling point
Very high
Very strong covalent bonds throughout
Giant covalent lattice - electrical conductivity
Diamond - very low
No delocalised electrons or mobile ions
Graphite/graphene - very good
Delocalised electrons
Giant covalent lattice - solubility
Very low
Can’t interact with water
Graphene
Single layer of graphite
Delocalised electron on surface - conduct
Anamalous properties of water
Liquid denser than solid
H bonds hold molecules apart in solid
Strong H bonds
Higher mp than expected
Volatile
High bp = low volatility
