physical properties Flashcards
intramolecular bond
bond which occurs BETWEEN atoms INSIDE molecules
intermolecular forces
forces of attraction BETWEEN molecules,ions,atoms,noble gases
van der Waals forces
intermolecular forces of varying strength specifically between molecules
london force
weakest van der Waals force
due to the attraction of electrons of one molecule between to the nuclei of another
exists between non polar molecules
hydrogen bond force
force between highly polar molecules which is a special case of van der Waals forces between polar molecules
stronger than forces between other polar molecules
interaction
bond/force between particles (atoms,molecules, ions,electrons) of substance responsibility for its physical properties
melting and boiling points
depends on strength and number of interactions betel particles
more,stronger forces= higher MP + BP
conductivity
ability for current to flow through substance
substance must contain charged particles (ions,electrons) that are free to move
malleable
bendability
hard materials ability to be hammered/ pressed into shape w/o breaking/cracking
brittle
hard material that will break/crack when subjected to force.
types of solids
metallic lattice
ionic lattice
molecular lattice
atomic lattice
what are the particles in a metallic lattice
positive kernels and delocalised electrons
how is a metallic lattice formed
it is a result of metallic bonding
metallic lattice strength
strong, generally hard
metallic lattice MP+BP
high MP and BP
- many strong electrostatic forces of attraction between positive kernels and delocalised electrons
- more energy need to overcome forces of attraction
metallic lattice conductivity
good conductors of electricity in all phases
- delocalised electrons can move over positive kernels
metallic lattice malleability
sheets of cations can slide over each other but remain held together by electrostatic forces of attraction between electrons and cations
ionic lattice strength
strong
ionic lattice particles
anions and cations
MP + BP ionic lattice
high
many strong electrostatic forces of attraction between anions and cations
more energy needed to overcome forces
why one w greater BP - ionic lattice
electrostatic forces between - are stronger than those between - bcus the size of the charges are greater in -
more energy required to overcome forces
ionic lattice brittle
a shift in the arrangement of ions brings like charges alongside each other which result in a force of repulsion which causes the solid to fracture
conductivity ionic lattice
in solid state, cations and anions are not free to move to carry charge in ionic lattice
-cannot conduct electricity in solid state
when can ionic lattice conduct electricity
aqueous state/molten state
-ions are free to move to carry charge
molecular lattice particles
molecules held together by electrostatic forces
van der waals forces from weak to strong
london forces of attraction
dipole dipole forces of attraction
hydrogen bond force
strength molecular lattice
generally weak when compared
london force bond
electrons randomly move around molecule
at a point in time e-‘s can exist on one side more
metallic lattices conduct electricity in solid state
The lattice contains delocalised electrons which are free to move to carry charge
Explain why metallic lattices have generally high melting points
◦There are many, strong electrostatic forces between cations and delocalised electrons in the lattice
◦More energy is required to overcome these forces
Explain why aluminium has a higher melting point than magnesium.
◦Both substances are metallic
◦Aluminium cations have a 3+ charge and magnesium cations have a 2+ charge ◦The electrostatic forces of attraction between the cations of aluminium and the
delocalised electrons are stronger than those in magnesium
◦More energy is required to overcome the stronger forces in the aluminium lattice ◦Therefore aluminium has a higher boiling point than magnesium
Explain why metals are malleable.
◦The sheets of positive cations can slide over one another while the electrostatic forces mm
between the cations and delocalised electrons remain intact ◦The lattice can be bent into different shapes
why ionic lattices cannot conduct electricity in the solid state.
◦The ions (cations and anions) are not free to move to carry charge in the solid state
Why are ionic substances brittle?
◦When a force is applied to the ionic lattice the arrangement of the ions can change so that like charges are next to each other.
◦Like charges repel each other ◦The lattice shatters
Explain why ionic substances generally have a high melting point.
◦There are many, strong electrostatic forces between cations and anions in an ionic lattice
◦More energy is required to overcome these forces
Which substance would have a higher melting point? Magnesium oxide or lithium bromide.
Both substances are ionic
◦In magnesium oxide the cations have a 2+ charge and the anions have a 2- charge
◦In lithium bromide the cations have a 1+ charge and the anions have a 1- charge
◦The electrostatic forces of attraction between ions (cations and anions) are stronger in
the magnesium oxide lattice as a result
◦More energy is required to overcome stronger forces ◦Magnesium oxide has a higher boiling point than lithium bromide
) Do atomic lattices have generally high or low melting points. Explain fully.
◦High melting point
◦Many strong covalent bonds holding atoms together ◦More energy is required to break these bonds.
Which has a higher melting point? Diamond or graphite? Explain fully.
◦Diamond
◦Each carbon atom is bonded 4 times with other carbons compared to graphite
where each carbon atom is bonded only 3 times with other carbon atoms ◦More energy is required to break the many strong covalent bonds in diamond
) Which atomic lattice can conduct electricity in the sold phase? Explain.
Graphite
◦Each carbon atom has a delocalised electron that is not bonded ◦These electrons are free to move to carry charge
london force origin
Electrons move randomly around particles
By chance one molecule can form a temporary dipole
When this temporary dipole comes close to a neighbouring molecule the
neighbouring molecule forms an induced dipole
The two dipoles electrostatically attract
hydrogen bond force origin
when a small highly electronegative atom( N,O,F) bonds with hydrogen, hydrogen bonding can occur
THE highly electronegative atom attracts the bonding pair of e- away from hydrogen exposing a naked proton
the naked proton electrostatically attracts the lone pair of e- of a neighbouring molecule
molecular lattice MP/BP
low
weak van der waals forces between molecules
less energy required to overcome forces
molecular lattice conductivity
cannot conduct electrical charge
neutral molecules
no charges to move to carry charge
molecular lattice phase change
intermolecular forces overcome
molecular lattice chemical change
intramolecular bonds broken
atomic lattice types
diamond
graphite
silicon dioxide
atomic lattice strength
extremely strong
many strong covalent bonds between atoms
more energy needed to break the bonds
diamond bonds per atom
4
graphite bonds per atom
3
silicon dioxide bonds per atom
bonds per atom
graphite
covalent bonds between atoms
sheets of carbon held together by weak electrostatic forces of attraction- london forces
held by delocalised e- - can conduct electricity
why silicon dioxide poor conductor
atoms are neutral
no particles to move to carry charge
what influence strength of intermolecular forces
the type of intermolecular force involved e.g.: weak van der Waals forces (such as
London forces) vs stronger hydrogen bonds.
• The number of electrons in the molecule which is indicated by the molar mass of the
molecule (for London forces only).
• The number of intermolecular forces (relates to hydrogen bonds only)
