elements of life Flashcards
(55 cards)
what is the relative mass and charge of a proton?
relative mass= 1
relative charge= +1
what is the relative mass and charge of a electron?
relative mass= 0.0005
relative charge= -1
what is the relative mass and charge of a neutron?
relative mass= 1
relative charge= 0
what does the mass number tell you?
total number of protons and neutrons in the nucleus
what does the atomic number tell you?
number of protons
what are isotopes?
- atoms of the same element with different mass numbers
- same number of protons, different number of neutrons
what is the history of the atom in order?
- DALTON
- JJ THOMPSON
- RUTHERFORD
- BOHR
- CHADWICK
what was dalton’s theory of the atom?
invisible spheres
what was JJ Thomson’s 1897 theory of the atom?
- discovered atoms weren’t solid
- discovered electrons
- PLUM PUDDING MODEL = ball of positive matter with negative electrons differed evenly throughout
what was Rutherford’s 1909 discovery of the atom?
- GOLD FOIL EXPERIMENT
= fired alpha particles (positively charged) at a thin sheet of gold foil - most alpha particles passed through, showing most the atom is empty space
- some alpha particles deflected back, showing a small DENSE nucleus
- some alpha particles deflected at an angle, showing nucleus is positive
what was Bohr’s 1932 model of the atom?
- electrons exist in fixed shells
what is Ar / relative atomic mass?
a weighted average taking into account the abundance of all isotopes
what is mass spectroscopy?
mass spectroscopy is a technique that can tell is the % abundance of isotopes of elements, which allows us to calculate Ar
what are the steps of mass spectroscopy?
1) sample is vaporised (turned into gas)
2) IONISATION- the gas particles are bombarded with high energy electrons to produce a cation
3) ACCELERATION- the positive ions are accelerated by an electric field
4) DETECTION- time taken for positive ions to reach the detector is measured.
light, highly charged ions reach the detector 1st, heavier ions take longer
how do you calculate Ar?
(relative isotopic mass x relative atomic abundance) / 100
what is Avogadro’s constant?
6.022 × 10^23
what is 1dm^3 converted to cm^3
1000cm^3
what is empirical formula?
the simplest ratio of atoms
why is the actual yield normally less than the theoretical yield?
- not all ‘starting’ chemicals fully react
- some chemicals are lost
what are titrations used for?
to find out the CONCENTRATIONS of acid or alkali solutions
- allow you to find out exactly how much acid is needed to neutralise a quantity of alkali
what are the steps of a titration?
1) Measure out some alkali using a pipettes and put into a flask, along with drops of indicator
2) Fill a burette with acid
3) Do a rough titration, for an idea of where the end point is. To do this take an initial reading to see how much acid is in the burette. Then add yeast acid to alkali, whilst swirling the flask. Stop when there is a colour change (end point) Record final reading
4) For an accurate titration, add the acid dropwise near the endpoint.
5) Work out the amount of acid used to neutralise the alkali.
6) Repeat and work out mean of concordant results
how to get an accurate titration?
- use a white tile
- drop wise towards endpoint
what is fusion?
fusion is the forcing together of 2 LIGHTER NUCLEI to make 1 HEAVY NUCLEI and hence a new element
what conditions does nuclear fusion require?
in order to overcome the repulsion of 2 positive nuclei:
-very high temperatures
-very high pressure
