Topic 2: Bonding And Structure Flashcards
Ionic bonding definition
The electrostatic forces of attraction between oppositely charged ions
features of ionic compounds
- giant ionic structure
- most ionic compounds dissolve in water
- conduct electricity when molten
- have high melting points due to many electrostatic forces of attraction
what happens to the melting point of ionic compounds as size of charge on the ions increases
Bigger charge, stronger forces of attraction so more energy is required to overcome so higher melting point.
what happens to the strength of ionic bonds as size of ion decreases
Smaller ion, stronger electrostatic forces of attraction/stronger ionic bonding
Describe and explain trend in ionic radius moving down a group
- ionic radius increases down group
- number of electron shells increases so ionic radius increases
Features of graphite
- conducts electricity due to delocalised electrons
- high melting point due to strong covalent bonds
- insoluble due to covalent bonds being too strong to break
- layers slide easily due to weak intermolecular forces
Features of diamond
- rigid arrangement allows heat to conduct well
- very high melting point due to very strong covalent bonds
- doesn’t conduct electricity due to no delocalised electrons
- insoluble due to covalent bonds being too strong
Covalent bonding definition
The electrostatic forces of attraction between the shared electrons and positive nuclei
Dative covalent bonding
Both electrons come from one atom. 2 electrons donated to form a bond.
Name of shape with 2 bonding pairs and 0 lone pairs
Linear. Angle 180 degrees.
Name of shape with 3 bonding pairs and 0 lone pairs
Trigonal planar. Angle 120 degrees.
Name of shape with 4 bonding pairs and 0 lone pairs
Tetrahedral. Angle 109.5 degrees
Name of shape with 5 bonding pairs and 0 lone pairs
Trigonal bipyramidal. Angle 90 & 120 degrees.
Name of shape with 6 bonding pairs and 0 lone pairs
Octahedral. Angle 90 degrees.
Name of shape with 3 bonding pairs and 1 lone pair
Trigonal pyramidal. Angle 107 degrees.
Name of shape with 2 bonding pairs and 2 lone pairs
Bent. Angle 104.5 degrees.
Name of shape with 5 bonding pairs and 1 lone pair
Square pyramidal. Angle < 90 degrees.
Name of shape with 4 bonding pairs and 2 lone pairs
Square planar. Angle 90 degrees.
Metallic bonding definition
The electrostatic forces of attraction between a metal cation and a ‘sea’ of delocalised electrons
Electronegativity definition
The ability for an atom to attract electrons towards itself in covalent bonds
Put the intermolecular forces in order from weakest to strongest
London forces<permanent dipole-dipole<hydrogen bonding
What happens to the solubility the longer a hydrocarbon gets
Longer hydrocarbon less soluble - stronger london forces between hydrocarbons as longer non-polar chain so greatly outweigh intermolecular forces between hydrocarbon and water.
Compare the amount of London forces between longer, straight hydrocarbons and branched hydrocarbons
Longer, straight hydrocarbons have more London forces (because more points of contact) so more energy is needed to overcome the forces and the boiling point increases. Branched hydrocarbons cant pack together so there are less (and weaker) London forces and lowers the boiling point.
Contrast the ionic radius between isoelectronic ions
Ionic radius in isolectronic ions decreases as atomic number increases
NCl3 has a higher boiling point than NF3. Why?
- Greater london forces in NCl3
- because NCl3 has more electrons than NF3
- Both have permanent dipole-dipole forces and dipole forces stronger in NF3
- Because F more electronegative than Cl
- London forces are most significant intermolecular force so more energy needed to overcome intermolecular forces between NCl3 than NF3
What is an orbital
A region/space in an atom in which there is a high probability of finding electrons of which can hold a maximum of 2 electrons with opposite spin
