Science - Chemistry - Bonding, Structure, and the Properties Of Matter - C2a Flashcards
what is an ion ?
a charged particle
do metal atoms lose or gain electrons ?
lose electrons
when are ions formed ?
when electrons are lost or gained
what type of ion does a metal atom form ?
a positive ion
do non metal atoms lose or gain electrons ?
gain electrons
what type of ion does a non metal ion form ?
a negative ion
how do you calculate the charge of an ion ?
protons - electrons
why are ions formed ?
atoms are trying to get a full outer shell and become stable
elements in the same group have what ?
the same number of electrons in their outer shell
when metals react with non metals what kind of bonding is this ?
ionic bonding
what is ionic bonding ?
oppositely charged ions that are strongly attracted to each other held together by strong electrostatic forces
what are the advantages of using a dot and cross diagram when showing ionic bonding ?
- useful for showing how ionic compounds are formed
what structure do ionic compounds have ?
a giant ionic lattice
what is an ionic compound ?
strong electrostatic forces of attraction between oppositely charged ions which act in all directions
what are the disadvantages of using a dot and cross diagram to display ionic compounds ?
- they do not show the structure of the compound
- they do not show the relative sizes of ions or how they are arranged
what are the advantages of using a 3-D model to display ionic compounds ?
-show relative sizes of ions
- show regular pattern in an ionic crystal
what are the disadvantages of using a 3-D model to show ionic compounds ?
- only lets you see outer layer of the compound
what are the disadvantages of using a ball and stick models to display ionic compounds ?
- ions aren’t shown to scale
- they suggest there are gaps between the ions, which there aren’t
how do you work out the formula of an ionic compound with a dot and cross diagram ?
count up how many atoms of each element there are
how do you work out the formula of an ionic compound using the ball and stick model ?
work out what ions are in the ionic compound then balance the charges of the ions so the overall charge on the compound is 0
what are the properties of ionic compounds ?
- high melting and boiling point due to strong electrostatic attraction between the ions
- solubility, most ionic compounds can dissolve in water
- do not conduct electricity when solid as they are in fixed positions but when melted or dissolved ions are free to move and they can carry electrical charge
what is covalent bonding ?
when a pair of electrons is shared between 2 atoms to get full outer shells
in what type of atoms do covalent bonds occur ?
non metal atoms
what are the advantages of using a dot and cross diagram to show covalent bonds ?
- shows which atoms the electrons in a covalent bond came from
what are the disadvantages of using a dot and cross diagram to show covalent bonds ?
- do not show relative sizes of atoms
- don’t show how they are arranged in space
what are the advantages of using displayed formulas to show covalent bonds ?
- shows how atoms are connected in large molecules
what are the disadvantages of using displayed formulas to show covalent bonds ?
- don’t show 3-D structure
- don’t show which atoms the electrons came from
what are the advantages of using 3-D models to show covalent bonds ?
- shows the atoms and their arrangement in space
what are the disadvantages of using 3-D models to show covalent bonds ?
- do not show the bonds
- can get confusing for large molecules where there are lots of atoms to include
- they don’t show where electrons in bonds came from
what are the advantages of using ball and stick models to show covalent bonds ?
- shows the bonds clearly
what are the disadvantages of using ball and stick models to show covalent bonds ?
- don’t show arrangement in space
how do you find the molecular formula ?
count up how many atoms of each element there is and write that number next to the element symbol
what are simple molecules ?
molecules that are made up of only a few atoms joined by covalent bonds
give an example of a simple molecule
hydrogen
what are the properties of simple molecules ?
- don’t conduct electricity
what are the melting and boiling points of simple molecules like ?
they are low, so generally gases and liquids at room temperature because despite strong covalent bonds, the intermolecular forces are weak so don’t take much energy to overcome
as molecules get bigger, what happens to the intermolecular forces ?
they increase- so the melting and boiling points increase
the large the molecules the melting and boiling points are what ?
higher
what is a polymer ?
long molecules made up of repeating sections joined by strong covalent bonds
what are the melting and boiling points of polymers like ?
higher than in simple molecules as the intermolecular forces are stronger but lower than ionic and covalent bonds, they are generally solid at room temperature
what is a giant covalent structure ?
giant structures that are bonded to each other by strong covalent bonds, they have high high melting and boiling points
what is an allotrope ?
different structural forms of the same element in the same physical state
what are the allotropes of carbon ?
- diamond
- graphite
- graphene
- fullerene
describe the structure of diamond
each carbon atom forms 4 covalent bonds with other carbon atoms, forming a rigid structure which is why diamond is so hard
what are the properties of diamond ?
- high melting point
- doesn’t conduct electricity
describe the structure of graphite
each carbon atom forms 3 covalent bonds
this creates sheets of carbon atoms arranged in hexagons
there are no covalent bonds between the layers so they are only held together by weak intermolecular forces
thismakes graphite soft and slippery so it is ideal as a lubricating material
only 3 out of each carbons 4 electrons are used in bonds so each carbon atom has 1 delocalised electron
what are the properties of graphite ?
- high melting point
- conducts electricity and thermal energy
describe the structure of graphene
a single sheet of carbon atoms joined together by hexagons- like a single layer of graphite it is 2-D
the covalent bonds in graphene are very strong but it is also very light so can be added to materials for strength without adding weight
it has delocalised electrons so could be used in electronics
what are the properties of graphene ?
- conducts electricity
what are fullerenes ?
hollow molecules of carbon, shaped in tubes or balls, mainly made up of carbon atoms arranged in hexagons but can also contain pentagons and heptagons
what is an example of a fullerene ?
- buckministerfullerene was the first fullerene, forming a hollow sphere containing 20 hexagons and 12 pentagons
- nanotubes are fullerenes which are tiny carbon cylinders, they’re good conductors of heat and electricity
what are the uses of fullerene ?
-medicine- to cage other molecules, the fullerene structure forms around another molecule which is then trapped around another molecule which is then trapped inside , could be used to deliver a drug where it is needed in the body in a controlled way
- catalysts- fullerenes have large surface areas so could help make industrial catalysts
- lubricants- coating moving machine parts in fullerene helps reduce friction
- strengthening materials- nanotubes have high strength without adding too much weight
- electronics- nanotubes can conduct electricity and are small so could be used in small circuits
what does delocalised mean ?
an electron that isn’t associated with a particular atom or bond and is free to move within a structure
what is metallic bonding ?
the attraction between metal ions and delocalised electrons in a metal
what are the properties of metals ?
- high melting and boiling points
- good conductors of electricity
- malleable
what is an alloy ?
a mixture of 2 or more metals or a metal and another element
why are alloys said to be more useful than pure metals ?
they are harder
why are alloys harder than pure metals ?
different elements have different sized atoms so when another element is mixed with a pure metal, the new element will distort the layers, making it harder for them to slide over each other
what are the 3 states of matter ?
- solid
- liquid
- gas
what is the strength of forces between the particles determined by ?
- the material
- the temperature
- the pressure
what determines which state a material is in ?
how strong the forces of attraction are between the particles of the material
what kind of force of attraction is there between solid particles ?
a strong force of attraction
what are solid particles ?
particles in a fixed position, forming a very regular arrangement- particles don’t move from their positions and have a definite shape and volume
what kind of force of attraction is there between liquid particles ?
weak forces of attraction
what are liquid particles ?
particles that are randomly arranged and are free to move past each other, they have a definite volume but not a definite shape
what kind of force of attraction is there between gas particles ?
very weak forces of attraction
what are gas particles ?
particles are free to move, and do so constantly in a random motion, they travel in straight lines until they collide with another particle. The particles are very far apart, gases don’t have a definite volume or shape
what happens to gases when the temperature increases ?
the faster the particles will move so they will hit other particles of the sides of a container more often and harder, causing the pressure of the gas to increase, or if the container isn’t sealed the volume of gas will increase
what happens to liquids and solids when the temperature increases ?
they expand slightly, solids vibrate
what are the state symbols for solids, liquids, gases and aqueous ?
solid - s
liquid - l
gas - g
aqueous - aq
