Intra Bonding Flashcards
define metallic bonding
electrostatic forces of attraction between cations and the sea of delocalised electrons that hold the cations in a metallic lattice structure
what does it mean for metallic bonds to be non-directional?
electrons in the metallic lattice are delocalised and do not belong to any particular cation
describe why a metallic lattice forms
- metal elements have low ionisation energies compared to non-metal elements
- metal atoms lose their valence electrons, such that they are free to move among the cations formed during ionisation
- metallic bonding, hence held in a metallic lattice
what does the strength of metallic bonding depend on?
- charge of positive ions
- size of positive ions
- way cations organised in the metallic lattice
state the physical properties of metallic substances
high melting and boiling points
strong
good thermal conductor
electrical conductor
malleable and ductile
why do metallic substances have high MP/BP/Strong?
- In a metallic substance, there are strong metallic bonds within a metallic lattice
- large amount of energy/force needed to overcome/disrupt these metallic bonds
- high melting point/strong
define malleable and ductile
malleable: able to be bent into sheets
ductile: able to be drawn into wires
why are metallic substances malleable and ductile?
when sufficient force is applied to the metallic substance,
- layers of positive ions move relative to one another
- there will still be metallic bonds (define) between sea of delocalised electrons and positive ions
- this is because metallic bonds are non-directional (define)
- metallic substance’s shape can be deformed while still maximising the metallic bond
Malleability / ductility 1Metallic bonding consists of a sea of delocalised electrons surrounding
positive metal ions 1This bonding is non-directional 1Therefore if a force is applied, the metal can change shape without
disrupting the bonding
Why are metallic substances electrical conductors?
- to conduct electricity, there must be mobile, charged particles present
- metallic substance, sea of delocalised electrons are mobile, charged particles, hence can conduct electricity
Why are metallic substances good thermal conductors?
- thermal conduction is a result of KE being transferred when 1 particle collides with its neighbouring particle
- sea of delocalised electrons are free to move through the lattice, can transfer kinetic energy rapidly though the lattice
define an alloy and state its metallic structure
- mixture of a metal and another metal or a non-metal
- same as metallic substance, but impurity atoms are incorporated into the lattice
how does an impurity atom increase hardness and strength of the alloy?
- impurity atoms disrupt the orderly nature of the metallic lattice
- make it more difficult for the layers of positive ions to slide over one another if the metal is bent
- increase hardness and strength
define ionic bond
electrostatic forces of attraction between positively charged ions and negatively charged ions in an ionic crystal lattice structure
why is the ionic lattice held together so closely?
electrostatic forces of attraction between oppositely charged ions are greater than electrostatic forces of repulsion between like charged ions in the ionic crystal lattice, held together strongly
describe a NaCl lattice
- made up of a continuous lattice of alternating Na+ and Cl-
- each Na+ surrounded by 6 Cl-
why do ionic substances have high MP/BP/Strong?
- In an ionic substance, there are strong ionic bonds within a ionic crystal lattice
- large amount of energy/force needed to overcome/disrupt these ionic bonds
- high melting point/strong
why are ionic substances brittle?
if sufficient force is applied,
- forces ions with like charges to lie adjacent to each other
- electrostatic forces of repulsion between like-charged particles cause it to fracture
- brittle due to the directional force between positively charged and negatively charged ions in ionic crystal lattice
Magnesium sulfide consists of a **rigid 3D lattice **composed of ions. 1
When a force is applied this causes like charges to align / causes disruption of the lattice structure. 1
The similarly charged ions then repel, causing the lattice to shatter. 1
why can’t ionic substances conduct electricity in solid?
- to conduct electricity there must be mobile charged particles
- positive and negatively charged ions are not free moving as they are held in the rigid 3D lattice
- cannot conduct electricity
why can ionic substances conduct electricity in molten/aqueous?
- ionic substances dissociate into their ions and break away from rigid lattice
- charged, mobile particles now present to conduct electricity
why do metals form cations and non-metals form anions?
- metals tend to lose electrons because of their low IE
- non-metals tend to gain electrons because of their high EN
define covalent bonds
forces of attraction formed when 1 or more of the pairs of electrons are shared between 2 atoms to achieve stable electron configuration
why do covalent molecular have low BP MP/soft
weak intermolecular forces of attraction between discrete molecules, small amount of energy needed to to overcome/disrupt weak bonds
covalent molecular electricity
pure form - non-conductors of electricity because no mobile charged particles
some ionise in solution - acids, bases, HF, CH3COOH, NH3
covalent network high BP/strong
- In an covalent network substance, there are strong covalent bonds within a covalent network lattice
- large amount of energy/force needed to overcome/disrupt these covalent bonds
- high melting point/strong
describe diamond structure
each C covalently bonded to 4 other C in a tetrahedral arrangement, covalent network lattice
diamond cannot conduct electricity
each C covalently bonded to 4 other C in a tetrahedral arrangement, covalent network lattice valence electrons all valence electrons are localised to the covalent bonds, no mobile charged particles
diamond hard and brittle
high melting point, if diamond was subjected to extreme stress and one part of the lattice is disrupted, place stress on the rest of the lattice causing it to fracture - brittle
describe graphite structure
covalent layer lattice, each C covalently bonded to 3 other C in hexagonal graphene sheets
weak intermolecular forces between graphene layers
1 delocalised electron per carbon atom
graphite conductor of electricity
each C provides 1 delocalised valence electrons (charged mobile particle)
graphite lubricant
slippery, layers slide easily, dry lubricant
amorphous carbon
irregular structure of carbon atoms, many varieties exist with many different non-continuous packing arrangements
silica structure
covalent network substance, each silicon atom bonded to 4 oxygen atoms in a tetrahedral arrangement
fullerene structure
atoms are arranged in a series of pentagons and hexagons, each C covalently bonded to 3 C
