EL 1, 2 Flashcards
`why are models useful / not useful
- they are useful because they help explain observations
- they are not useful because they cannot be considered as the truth
what are the names and charges of each of the subatomic particles that make up an atom
- proton +1
- neutron 0
- electron -1
what are the locations of each of the three types of subatomic particles
- proton, makes up the nucleus
- neutron, makes up the nucleus
- electrons, orbit the nucleus
what are the masses of each of the subatomic particles
- proton, 1
- neutron, 1
- electron, 0.00055
what is the atomic number of an atom
(Z)
- the number of protons in the nucleus
- is numerically equal to the charge
how do you calculate mass number
atomic number (Z) + number of neutrons (N)
define isotope
atoms of the same element with different mass numbers
what is the relative atomic mass of an element
- since most elements naturally exist as a mixture of isotopes
- relative atomic mass is an average of all the relative isotopic masses taking their abundances into account
how do mass spectrometers work
- the sample atoms or molecules are ionised to positively charges cations
- the ions are separated according to their mass to charge ratios
- separated ions are detected together with their relative abundance
describe the process of nuclear fusion
two light, atomic nuclei fuse together to form a single heavier nucleus of a new element, releasing enormous quantities of energy
- at normal temperatures on the Earth, the positive nuclei repel strongly
- at much higher temperatures (in a star) the nuclei move much more quickly and collide with so much energy that the repulsion is overcome
what is spectroscopy
- the study of how light and matter interact
what are the names of the two models used to describe the behaviour of light
- the wave theory
- the particle theory
describe the wave theory of light
- it’s one form of electromagnetic radiation
- light behaves like a wave with characteristics wavelength and frequency
- a wave of light travels the distance between two points in a certain time
- speed of light is the same for all waves of different wavelengths
what is different about light of different colours
- it has different wavelengths and therefore different frequencies
how are frequency and wavelength related
wavelength (m) X frequency (^-1) = speed of light
define the particle theory of light
- easier to explain by thinking of the waves as particles
- light is a stream of photons (tiny packets of energy)
- energy of the photons is related to position of light in the electromagnetic spectrum
how do you calculate energy of a photon
- Energy of a photon = planck constant X frequency
what is the value of Planck constant
6.63 X 10^34
why can a hydrogen atom only emit a limited number of specific frequencies
- when an atom is excited, electrons jump to a higher energy level
- later they drop back down to lower energy levels and emit the extra energy as electromagnetic radiation giving off an emission spectrum, giving am emisison spectrum
what happens when white light is passed through a cool sample of a gaseous element
- black lines appear
- the black lines that appear in the absorption spectrum correspond to light absorbed by the atoms
what do the intensities of of the lines on the atomic spectra correspond to
- the abundance of the elements
what were the main parts of Bohr’s theory
- the electron in the hydrogen atom only exists in definite energy levels
- a photon of light is emitted or absorbed when the electron changes energy levels
- the energy of the photon is equivalent to the difference between energy levels
- E = hv so frequency of the emitted or absorbed light is related to the energy by thus equation
what does it mean that the electrons energy is quantised
- the energy of an electron cannot change continuously
- it isn’t able to change to any value
- only the definite values that are allowed
what’s the name of of the electrons lowest energy level, and what happens as the energy levels get further from the nucleus
- the ground state
- energy levels increase
describe the Lyman series
- frequencies of the lines of the Lyman series correspond to changes in electronic energy from various upper levels to one common lower level
what does Bohr’s theory explain
- explains how you get an absorption spectra and emission spectra
- gives scientists a model for the electronic structure of atoms
- lent support to the new quantum theory
what are the ions for the following elements and the corresponding flame colours:
- lithium
- sodium
- potassium
- Li+ bright red
- Na+ yellow
- K+ lilac
what are the ions and the corresponding flame colours for the following elements:
- calcium
- barium
- copper
- Ca2+ brick red
- Ba2+ apple green
- Cu2+ blue green
why are flame tests carried out
- used to identify the presence of a metal in a sample
