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Flashcards in property and stucture of atoms / materials Deck (43)
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two things that affect ionisation energy

- increased nuclear charge (number of protons) = increased ionisation energy
- increased distance from nucleus = decreased ionisation energy


what is electronegativity

the ability of an atom to attract and form bonds with electrons (from nearby atoms)


what is atomic radius

distance between the nucleus and outer boundary shell (valence)


explain the trends as you go across the periodic table

- decrease atomic radius
- decrease atomic size
- decrease in metallic nature
- increase ionisation energy
- increase electronegativity


explain the trends as you go down the periodic table

- increase atomic radius
- increase atomic size
- increase metallic nature
- decrease ionisation energy
- decrease electronegativity


explain the function of mass spec

- measures the masses and relative concentration of atoms and molecules
- determines elements / isotopes that are present and isotope concentration / relative abundance


explain the process of mass spec

- substance to be analysed is vaporised and ionised (overall positive charge)
- ions are accelerated
- pass through a velocity selector and then enter the magnetic field
- particles are separated based on mass / charge ratio


explain the analysis of results for mass spec

- mass / charge ratio and relative abundance are recorded on the output chart


explain the function of the flame test

- identifies a range of metal ions due to the characteristic colours produced when their salts are burnt


explain the process of flame tests

- samples placed in a hot non-luminous flame give characteristic colours
- due to the electrons moving from ground to excited state and the amount of energy


explain the function of AES

- a more efficient and quantitative method of analysing elements in a flame


explain the process of AES

- intense heat of flame atomises and vaporises sample
- excited atoms emit light
- dispersed through a prism into its characteristic spectra with the monochromator allowing each wavelength to be detected and recorded separately


explain the analysis of results for AES

- produces a series of electron energy levels (wavelengths) where the darkness and intensity of the wavelengths allows us to identify more metalloid elements


explain the function of AAS

- used to determine how much of an element is present in a sample of a substance


explain the process of AAS

- light from the hollow cathode lamp has the specific wavelengths that the metal being analysed can absorb
- the detector effectively measures the amount of light which is absorbed
- this indicates the concentration of the metal atoms in the sample


explain the analysis of results for AAS

- produces a calibration curve
- absorbance value of known concentrations can be placed on the curve, the a.v of the unknown is compared
- properties and structure of materials is identified


what are pure substances

- uniform on composition
- element: made up of only one atom, can't be separated into simpler substances
- compound: made up of two or more different elements chemically combined into a fixed ratio


what are mixtures

- various compositions / impure substances
- homogenous: uniform composition and properties (becomes one / equal amounts when distributed)
- heterogenous: variable composition and properties (different amounts of substances when distributed)


what is a physical property

- properties that can be determined without changing the chemical composition of a substance
- examples: melting / boiling point, hardness, electrical conductivity, hardness, malleable, ductile, strength, state


what is a chemical property

- relate to the ability of a substance to react to form new substances
- example: decomposition by heat, effect of light, reactions with: water, acids, bases, oxygen etc


what is nanotechnology

- field deals with matter at the atomic and molecular scale, used in medicine, materials fabrication, energy production and electronics


what are nano-materials

- materials that have particles between 1-100 nanometers (nm) in size
- made of nanoparticles and nanoatoms (nano = x10^-9)


what is a nanometre

- 1 billionth of a metre, cannot be seen with the naked eye or by light microscopy
- small particle size results in unexpected and unique properties, different to those of bulk materials


what does delocalised mean

- electrons that are detached from their atoms


what does non-directional mean

- electrons of metallic bonds are free to move around between cations


what does malleable and ductile mean

- malleable: able to be beaten into another shape or flattened into a thin sheet without breaking
- ductile: able to be drawn into a wire


describe the structure of metallic bonding

- electrostatic attraction between the positive metal ions and the delocalised negative electrons


describe the properties of metallic bonding

- conduct electricity
- conduct heat
- ductile / malleable
- high melting / boiling point
- lustrous
- hard


describe the structure of ionic bonding

- 3D lattice of alternating positive and negative ions, which vibrate about their fixed positions, with a strong electrostatic attraction between positive and negative ions


describe the properties of ionic bonding

- hard
- brittle
- high melting / boiling point
- electrical conductivity: solid (no), molten state / solution (yes)