AOS 1-How can knowledge of elements explain the properties of matter? Flashcards
what is a nanoparticle?
are a specific type of nano-material with a range of applications and unique properties
what is a nano-material?
general term for materials of the nano-scale
how big/small are nano materials/particles? provide measurement and units used
they are measured in nanometers, nm (10^-9 meters). they can range from 1-100nm
what can nano materials be used for? (three things)
adsorption, transportation, catalysts
how do nano materials differ from those of the same material in bulk form?(properties)
very small, can be used for adsorption, transportation and as catalysts
what is an important feature of nano-materials?
their high surface area to volume ratio
what are the names of the two processes used when forming nano-materials?
bottom up, top down
what is an element? Give 5 examples
it is a substance made up of only one type of atom. eg, hydrogen, helium, uranium, radium, phosphorous
what’s a compound? give example
are substances made up of different elements in fixed ratios
what is an atom?
they’re the basic building blocks of matter
what is a subatomic particle? name them
a particle which makes up an atom.
they are protons, neutrons and electrons
what is a proton?
a subatomic particle with a positive charge
what is a neutron?
a subatomic particle with no charge
what is an electron?
a subatomic particle with a negative charge
what is a nucleus?
it is the centre of the atom and determines the atomic mass. it is made up of protons and neutrons
what is electrostatic attraction?
the force of attraction between a positively charged particle and a negatively charged particle
what is a molecule?
particle made up of 2 or more atoms. E.g includes O2, H2O
what is a chemical symbol?
a symbolic representation of an element, one or two letters, first letter is always capitalised and the second one must be lower case
what is an atomic number?
a numeric representation of the number of protons in an element
what is a mass number?
a numeric representation of the number of protons and neutrons in an element
what is atomic notation?
shows the atomic number, mass number and chemical symbol
what is an isotope? give examples
a variant of an element that has the same number of protons but different numbers of neutrons. common isotope is carbon, with isotopes carbon-12, carbon-13, carbon-14
what is a valence electron?
an electron found in the valence shell; an outermost electron in an atom or ion.
what is the atomic theory?
1802, English scientist John Dalton presented the first atomic theory of matter. He proposed that all matter is made up of atoms, which cannot be destroyed or divided any further
what is electronic configuration?
a way of representing the number of electrons in each shell (shell model).
what is the Bohr model
Bohr model was the first atomic model to explain the origin of emission spectra.
Bohr model assumes that electrons can only exist in fixed, circular orbits of specific energies. Orbits later came to be known as energy levels or shells
what does it mean when an atom is in its “ground state”?
a term used to describe an atom in which the electrons occupy the lowest possible energy levels because they don’t have excess energy
what does it mean when an atom is in an “excited state”?
a term used to describe an atom in which electrons occupy higher energy levels than the lowest possible energy levels because they have more energy
what is an emission spectra? describe it
it is a black rectangle with coloured lines. coloured lines are produced from electromagnetic radiation from elements. Emission spectra is unique for all elements
what is the Schrodinger model? describe it
is a model which describes the behaviour of electrons in atoms.
compare and contrast the Bohr and Schrodinger model
differences:
- Bohr saw electrons as hard tiny balls but schrodinger saw them as having wave like properties
- bohr thought electrons followed one directional orbit around the nucleus while schrodinger thought they vibrated/moved around a 3D space known as orbital
what is an orbital?
a region of 3D space that surrounds the nucleus in which an electron can be found
what is a shell?
are also known as energy levels
what is the periodic table?
a table where elements are organised according to their atomic number
describe the features of the periodic table
- elements are arranged in order of increasing atomic number
- main group elements; 1,2,13-18
- transition metals ; 3-12
what are groups?
they are the columns of the periodic table. elements in the same group will often have similar properties
what are periods?
they are the rows of the periodic table. can provide information on electronic configurations
what are blocks?
there are 4 main blocks, s,p,d,f. they are arranged according to their electron sub shell arrangement. eg, if the last sub shell an electron occupies is 2s2 then it will be in the s block
what are halogens?
they are the elements in group 17, they are very reactive
what is the core charge? how do you find it? what is the trend in the periodic table?
it is the attractive force felt by valence electrons towards the nucleus, the higher the charge the stronger the attraction. it increases from left to right.
core charge=(protons) - (number of inner shell electrons)
what is electronegativity? what its the trend? explain
it is the atoms ability to attract electrons. it increases up and across(L-R) the table
what is atomic radii? explain the trend
it is the distance from the nucleus out to the outermost electron shell. it increases down a group and DECREASES from left to right
what is first ionisation energy? explain the trend
it is the energy required to remove the outermost electron. it increases up and across (L-R) the periodic table.
what is metallic character? describe the trend
it is the metallic character and properties of elements. increases down and decreases across(L-R).
what is the reactivity of metals? describe the trend
it is the way metals react with water, or an indication of how easily an atom of that element loses or gains electrons. it increases down and right to left of the periodic table.
what is the reactivity of non-metals? describe the trend
it is the reactivity of non-metals with solutions. will increase up and across (L-R) the table
what are some common properties of metals?
high boiling/melting point and temperatures, good conductors of electricity, malleable and ductile, high density, lustrous, low electronegativities, low ionisation energies
what kind of structure do metals form? describe this structure
metals form a lattice structure. positive ions occupy fixed positions and are surrounded by a sea pf delocalised electrons
why do metals have high melting and boiling points?
lattice structure is held together by a strong force of electrostatic attraction and so a lot of energy is required to break these intermolecular bonds
why are metals good conductors in solid state?
metals have delocalised electrons! remember, electricity is the movement of electrons
why are metals good conductors in liquid state?
metals have delocalised electrons! remember, electricity is the movement of electrons
why are metals malleable and ductile?
when a force is applied to metals, they will move positions(change shape), the electrons keep them together
why do metals have high densities?
the lattice is tightly packed due to the bonds created by attraction
why are metals lustrous?
the light gives metals a bit of energy. this causes electrons to move up and down electron shells, they release photons which is the shiny stuff we see
why do metals have low electronegativities?
metals have few valence electrons so they are more likely to lose electrons than to gain them.
why do metals have low ionisation energies?
metals have few valence electrons so it is easy to remove them
describe the lattice structure of metals
positive ions occupy a fixed space, and are surrounded by a sea of delocalised electrons. force of electrostatic attraction holds them together
what are transition metals? what makes them different to main block metals?
they are elements which have unfulfilled d-subshells.
they tend to be harder, denser, higher melting point, strong magnetic properties
what is the metallic bonding model?
in this model, positive cations are surrounded by a sea of delocalised electrons.
-delocalised electrons come from valence shells
what are the limitations of the metallic bonding model?(what can’t they describe?)
cannot explain the range of melting points, hardness and densities of different metals, different conductivities, magnetic nature
use the bonding model to describe the following:
- malleability
- high melting/boiling points
- conductivity
malleability; attractive forces must be stronger than repulsive forces, the layers of ions are held together due to the delocalised electrons
high melting/boiling points; forces between particles must be strong, lots of energy is required to separate bonds in the lattice
conductivity; there must be a way of quickly transferring energy through a metal object, free moving delocalised electrons will move towards a positive electrode and away from the negative electrode
describe the reactivity of metals in water and describe the trend
group 1 metals are more reactive than group 2 metals. reactivity increases down a group
describe the reactivity of metals in acid an describe the trend
group 1 metals are more reactive than group 2 metals. reactivity increases down a group
describe the reactivity of metals in oxygen and describe the trend
group 1 metals react rapidly with oxygen, group 2 is also reactive with oxygen but heat is often needed to start reactions
what is iron ore?
it is composed mainly of iron oxide combined with rocky material. it is a mineral that occurs in earths crust
what form is iron ore usually found? give its chemical formula
it is usually found in the form hematite, Fe2O3
what are the three raw materials used to extract iron ore?
iron ore, coke, limestone
where does the extraction of iron ore take place?
extraction takes place in a bottle shaped tower called a blast furnace
how can the extraction of iron ore affect the environment?
there can be a loss of landscape due to mining, processing and transporting raw materials. air pollution, disposal of slag and noise pollution
what is an alloy?
they are modified metals which are more useful
how can metals be modified? name the three ways
annealing, quenching and tempering
what are the two types of alloys?
interstitial and substitutional alloy
what is an interstitial alloy?
an alloy where significantly smaller atoms are added to the metal. atoms will sit between larger atoms. carbon steel is an eg
what is a substitutional alloy?
an alloy where atoms that are added replace some of the parent metal atoms. eg stainless steel
what is the difference between an interstitial and substitutional alloy?
interstitial alloy has smaller atoms being added but substitutional alloys have larger atoms being added, they are about the same size as parent metal atoms
what are crystals?
are a region in a solid where particles are arranged in a certain way
what do smaller crystals indicate?
smaller crystals indicate harder and brittle metals
what do larger crystals indicate?
larger crystals indicate more malleable metals
what is heat treatment?
when heat is added to change the properties of metals
what is annealing?
when metal is heated to a moderate temperature and allows to cool slowly. larger crystals form and metal is softer with better ductility
what is quenching?
when metal is heated to moderate temperature and is quickly cooled. tiny crystals form and metal is mire hard and brittle
what is tempering?
a quenched metal is heated to a lower temperature than was used for quenching, and is allowed to cool. crystals of intermediate size form and metal is less brittle and hard
what sort of crystals form with quenching?
small, hard, brittle crystals
what sort of crystals form with annealing?
large, soft malleable crystals
what sort of crystals form with tempering?
intermediate crystals that are less hard and brittle
what are metallic nanomaterials?
are atoms arranged to make nano-sized structures
what is the ionic bonding model?
it is a model that describes the bonding between oppositely charged ions that are held together by electrostatic force of attraction, in a 3D lattice
use ionic bonding model to describe high melting and boiling temperatures of ionic compounds
the forces between particles are strong and so require lots of energy to break the forces.
use ionic bonding model to describe electrical conductivity in solid and molten state in ionic compounds
ionic compounds do not conduct electricity in solid state as there are no free electrons. they are conductive in a molten state however, because the bonds have been broken and there are free electrons.
use ionic bonding model to describe hard and brittle crystals
a strong force is required to move ions in order for them to break apart
what is an ion? give 2 examples
an ion is an atom which has lost or gained electrons. an example is calcium ion(loses 2 electrons to get positive charge) and nitrogen ion(gains 3 electrons to get negative charge)
what is an anion? give 2 examples
it is an atom which has gained electrons to get a negative charge. e.g fluorine and sulfur
what is a cation? provide 2 examples
it is an atom which has lost electrons to get a positive charge. e.g aluminium and potassium
what is Avogadro’s number? what is it used for?
it is used in a formula to help find the mole of a substance. it represents the amount of particles in one mole
what is a mole?
the amount of substance that contains the same amount of particles as there are in 12g of carbon
what is mass?
it is the amount of matter that an object contains
what is molar mass?
mass of one mol of a substance, measured in g mol-1
what is relative atomic mass?
it is the average weight of the masses of the isotopes of an element compared to carbon 12
what is relative molecular mass?
it is the mass of a formula unit compared to carbon 12
what is relative isotopic mass?
the relative mass of individual isotopes of each element compared to carbon 12
what is percentage abundance?
it is the percentage of a particular isotope that occurs naturally
what is empirical formula?
it is the simplest whole number ratio of a compound
what is molecular formula?
it is a formula which shows exactly how many atoms there are in a chemical formula
what are the two formulas used to find mole?
n=N/Na and n=m/M
what element are all elements compared to? why is this?
all elements are compared to carbon 12 because it weighs exactly 12 grams
what is percentage composition?
it is the percentage of an element within a compound
