property and stucture of atoms / materials Flashcards Preview

chemistry 11 > property and stucture of atoms / materials > Flashcards

Flashcards in property and stucture of atoms / materials Deck (43)
Loading flashcards...
1

two things that affect ionisation energy

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

2

what is electronegativity

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

3

what is atomic radius

distance between the nucleus and outer boundary shell (valence)

4

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

5

explain the trends as you go down the periodic table

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

6

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

7

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

8

explain the analysis of results for mass spec

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

9

explain the function of the flame test

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

10

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

11

explain the function of AES

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

12

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

13

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

14

explain the function of AAS

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

15

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

16

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

17

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

18

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)

19

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

20

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

21

what is nanotechnology

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

22

what are nano-materials

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

23

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

24

what does delocalised mean

- electrons that are detached from their atoms

25

what does non-directional mean

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

26

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

27

describe the structure of metallic bonding

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

28

describe the properties of metallic bonding

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

29

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

30

describe the properties of ionic bonding

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