Topic 2: Bonding, structure and properties of matter Flashcards
how do metals form ions?
by gaining or losing electrons
what is an ion?
a charged particle
what makes an atom stable?
if it has a full outer shell
if two electrons are lost what will be the charge of the atom? (if it had a full outer shell)
2+
what groups on the periodic table mostly form ions?
1,2,6,7
what determines what group an atom is in on the periodic table?
the number of electrons in the outershell
what is an ionic bond?
A bond between a metal and a non metal caused by the attraction between the two due to the ion of one being positive and the other negative
in a dot and cross diagram what are dots representative of?
electrons in a non metal
in a dot and cross diagram what are crosses representative of?
electrons in a metal
how can you tell if a dot and cross diagram is of a ion or not?
because when it is an ion there will be brackets around it with the charge written in the top right
what ion would sodium form? 2,8,1
2,8 electrons
draw the ionic bonding of magnesium and oxygen?
2 magnesium atoms with brackets and negative charge and electron structure of 2,8,8
1 oxygen atom with brackets and a 2+ charge with electron structure 2,8
what is an ionic compound?
a giant structure of ions they are held together by strong electrostatic attraction between oppositely charged ions these forces act in all directions in the lattice
all ionic compound have similar propitiates, name some of these properties?
high melting point high boiling point (due to many strong bonds between the ions)
cant conduct electricity
how do you work out the empirical formula of an ionic compound?
work out how to balance out the charge (eg if one of them has a + charge and the other has a 2- charge you will need two of the positives to counteract the negative) once you have worked this out put the amount you would need of each atom next to its formula
what the empirical formula of potassium and oxygen ions?
potassium forms + ions and oxygen forms 2- ions so you will need two oxygen and one potassium making the empirical formula:
k 2 0
what is a covalent bond?
when two non metal atoms join together and share a pair of electrons
why are covalent bonds very strong?
because the positively charged nuclei of the bonded atom are attracted to the shared pair of electrons by electrostatic forces
where do covalent bonds happen?
compounds of non metals and non metallic elements
how do you draw covalent bonding?
you draw the atomic structure of the atom but you let the dots (in this case as they are non metals) overlap to show that they are sharing electrons. in this case you should draw one of the elements with a crosses the other with dots
what is the molecular formula of this: h h / / h-c-----c-h / / h h
c2h6 as there are 2 carbons and 6 hydrogens
what other than a dot and cross diagram can be used to represent covalent bonding?
lines for each covalent bond
what are simple molecular structures?
made up of molecules containing few atoms joined together by covalent bonds
give 6 examples of simple molecular structures?
- Hydrogen
- chlorine
- oxygen
- hydrogen
- methane
- water
- hydrogen chloride
what are the properties of simple molecular structures?
- low boiling point-
- low melting point
- most are a gas/liquid at room temperature
- don’t conduct electricity as they do not have an overall electric charge
what is a polymer?
very large molecules linked by strong covalent bonds with relatively strong inter molecular forces and so they are solids at room temperature
what is the structure of a polymer?
lots of small units formed together to make a long chain
what is the molecular formula of poly(ethene)?
(C2H4)n
what are polymers at room temperature?
solid
what is an allotrope?
different structural forms of the same element in the same state
what are fullerenes?
molecules of carbon atoms with a hollow shape the structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms
why could fullerenes be used to transport drugs to the body?
because it can be used as a ‘cage’ due to the structure being circular or cube shaped
what is metallic bonding?
when there is a strong electrostatic attraction between the positive ions and the negative electrons which is what holds them together
what are the properties of metallic bonding?
- high melting point because of strong metallic bonding
- high boiling point because of strong metallic bonding
- conduct electricity because the delocalised electron carries charge
- conduct heat because energy is transferred by the delocalised electron
what state are metallic bonding at room temperature?
solid
why are metal malleable?
because the atoms can slide over one another
what is an alloy?
when more than one metal is mixed together
what are the three states of matter?
solid, liquid, gas
what does strong forces of attraction mean for solids?
it holds the solid together in a fixed position with a lattice arrangement
what are properties of a solid?
-keeps are definite shape and volume
what does a weak force of attraction do for liquids?
means they are randomly arranged and free to move past eachother
what are the properties of a liquid?
- they have a defied volume
- don’t have a defined shape
- particles move in a random motion the hotter it gets the more they move
what does a very weak force of attraction mean for a gas?
the particles are free to move and are far apart
what are the properties of a gas?
- don’t keep a defined shape
- don’t keep a defined volume
what is the particle theory for changes of state?
picturing every particle as a small spherical shape
what are the disadvantages of the particle theory?
- doesn’t show the forces between atoms so there is no way of knowing how strong they are
- particles are not spheres
what do physical changes not change?
the particle - just their arrangement or energy
what happens when a substance is heated?
the particles gain more energy so vibrate which weakens the force between them
what is melting point?
when a solid turns into a liquid
what is boiling point?
when a liquid turns into a gas?
what is condensing?
when a gas turns into a liquid
what is freezing?
when a liquid turns into a solid
what determines the amount of energy needed for a change of state?
how strong the forces between the particles are
which substance will be a liquid at room temperature:
melting point boiling point
oxygen -219 -183
nitrogen -210 -196
bromine -7 59
bromine
what is the formula of surface area to volume ratio?
surface area to volume ratio= surface area / volume
do nano particles have a high or low surface area to volume ratio?
high
what could nano particles potentially be used for?
- deoderants
- electric circuits
- sun creams
- as catalysts
what was the first fullerene to be discovered?
Buckminster fullerene (C60) which has a spherical shape
what are nanoparticles?
particles between 100 and 2500 nm
why can pure metals be bent and shaped?
because they are arranged in layers
why are alloys made?
because most metals are too soft for many uses so are made into alloys to be made harder
what is the structure of diamond?
each carbon atom forms four covalent bonds with other carbon atoms within the structure
what are the properties of diamond?
-hard
-high melting point
-high boiling point
-doesn’t conduct electricity
this is because each carbon atom forms four covalent bonds with other carbon atoms
what is the structure of graphite?
each carbon atom forms three covalent bonds with three other carbon atoms forming layers of hexagonal rings which have no covalent bonds within the layers
it has one delocalised electron from each carbon atom
how is graphite similar too other metals?
it has delocalised electrons
what is graphene?
a single layer of graphite
what was the first fullerene to be found?
buckminster fullerene (C60) which has a spherical shape
what are carbon nanotubes?
cylindrical fullerenes with very high length to diameter ratios
what are carbon nanotubes useful for?
nanotechnology, electronics and materials
what happens when a side of a cube decreases by scale factor 10?
the surface area to volume ratio increases by scale factor 10
where does metallic bonding occur?
in metallic elements and alloys
how can the structure of sodium chloride be represented?
-as NA+ ions and Cl- ions joined together in squares
-as small + ions and big - ions arranged as:
-+-+-+- but with circles around them
+-+-+-+
-+-+-+-
how can covalent structures be shown?
- circles sharing electrons
- molecular formulas with x and o written as electrons with no circles
- can be shown as - connecting molecules
- circles connected by tubes
what are the limitations of the ball and stick, dot and cross to represent molecules or giant structures?
dot and cross diagrams:
- dont show the relative of the atoms
- dont show how they are arranged in space
- as covalent bonds:
- dont show 3D structures
ball and stick:
-can get confusing quickly
what do metals consist of?
giant structures arranged in a regular pattern
how can the bonding in metals be represented?
- by positive circles with a negative excess circle
- by positive circles in a mass of minuses
how can solids, liquids and gases be represented?
solid: as a square with compact circles liquid: as a square with circles which do not fully join together gas: as a square with spaced out circles
what causes the melting and boiling point of a substance to change?
the strength of the forces between the particles. the strength depends on the type of bond and the structure of the substance
what are the limitations of the model of solids, liquids and gases when they are all in a square?
it doesn’t show the forces of attraction between them
what are the three states of matter shown as?
solid (s) liquid (l) gass (g) and aqueous (aq)
what are the structures of ionic compounds?
regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions
what are the properties of ionic compounds?
-high melting point
-high boiling point
because large amounts of energy are needed to overcome the many strong bonds
-can conduct when dissolved in water because the ions are free to move and flow
what are the inter molecular forces in small molecules?
weak intermolecular forces
it is the molecular forces that get overcome when it melts or boils not covalent bonds
intermolecular forces increase with size
what are the properties of giant covalent structures?
- solids
- very high melting points as there are strong covalent bonds
- silicon dioxide and diamond are examples
