1.1. atomic structure - mass spectrum

Question 1

the structure of the atom

Answer 1

electron in shells neutrons and protons in the nucleus

proton - mass 1 charge +1
neutron - mass 1 charge 0
electron - mass 1 / 1840 charge -1

Question 2

mass number

Answer 2

a
X

z
mass number = a and atomic number = z

Question 3

charge

Answer 3

atoms have no charge as the elctron charge balances out the proton charge

Question 4

ions

Answer 4

atoms that gain or lose electrons. can be positive , loses electron or negative gains electron

Question 5

isotopes

Answer 5

elements that have the different neutron number. they have the same chemical properties as they have the same electron configuration and the same proton number.
they may have different phyiscal properties e.g boiling point density, rates of diffusion etc.

Question 6

dalton

Answer 6

in the early 19th century dalton stated that atoms were solid spheres , different for each element

Question 7

j.j thomspon

Answer 7

. He proposed that atoms have structure similar to a plum pudding, with tiny, negatively charged electrons embedded in a positively charged substrate.

Question 8

rutherford

Answer 8

they charged postive alpha particles at a gold foil.
some of the alpha particles where delflected- a sign of a force of replusion. rutherford came up with the idea that the atom hard a dense nucleus at the centre which was postive and the rest of it was empty space as they were able to pass through.

Question 9

bohr

Answer 9

bohr noticed that electrond where in a cloud the atom would collapse if not so.
electrons were in energy shells the closer it is to the nucleus the lower the energy shell con fig.
electrons were in fixed positions.
in fixed obrit- nothing imbetween.
they can absorb electromagnetic energy and move up shells but can re emit electronmagnetic energy also e.g light.

Question 10

relative formula mass

Answer 10

average mass of atom

Question 11

mass spectromer

Answer 11

machine use to measure relative atomic/molecule mass of element or compound and abundancy.

Question 12

ionisation

Answer 12

the two ways are-
electrospray ionisation
electron gun ionisation

Question 13

electrospray ionisation

Answer 13

This is for larger molecules for example, glucose as it would be to large to knock an electron off it.

Question 14

how does electrospray ionisation work?

Answer 14

in this method the sample is dissolved in a solvent- water or methanol and is pushed through a small nozzle/ needle at high pressure. the nozzle should be able to conduct the high voltage that is applied to it this causes the mole

Question 15

what is the name of the solvent used in electrospray ionisation

Answer 15

water or methanol

Question 16

what kind of needle is used in electrospray ionisation

Answer 16

a fine hypodemic needle to give a fine mist.

Question 17

what is the needle attached to in electrospray ionisation

Answer 17

the tip of the needle is attached to the postive terminal of the high voltage power supply. the particles gain a proton

Question 18

what happens to the solvent

Answer 18

the solvent evaporates away while the ions xh + are attracted towards the negative metal plates where they are accelerated.

Question 19

what is electrospray known as

Answer 19

soft ionisation. fragmentation rarely takes place.

Question 20

electron ionisation

Answer 20

the sample is vaporised and then high energy elctrons are fired at it.

Question 21

where do the electrons come from in electron impact

Answer 21

the electrons come from an electron gun which is a hot wire filament with a current running through it and that emits electrons.

Question 22

what happens in electron impact

Answer 22

This usually knocks off one electron from each particle forming 1+ ions

Question 23

what happens to the ions in electron impact

Answer 23

they are attracted to the electric plate that is negative which are accelerated

Question 24

what ions are made

Answer 24

just 1+ ions

Question 25

what is electron impact used for

Answer 25

for elements or molecules with a low formula mass

Question 26

what happens to molecular ions

Answer 26

they form just 1+ ions. they often break down into smaller fragments which is detected by the mass spectrum .

Question 27

acceleration

Answer 27

the postive ions are accelerated by a negative electric field. the electric field provides the same kinetic energy to each ion.

Question 28

velocity

Answer 28

velocity depends on the mass of the element, the heavier the element the slower it is w

Question 29

what is the proportion of time and mass

Answer 29

the time of flight is protional to the square root of the mass of the ions

Question 30

stage 4 detection

Answer 30

the postive ion hits the negatively charged plate when they hit the detector the ions are discharged by gaining electrons from the plate.

Question 31

detection and movement

Answer 31

as movement takes place from the ions an electric current is produced and measured.The size of the current gives the number of ions hitting the plate.

Question 32

mass spectrum

Answer 32

a computer shows the mass to charge (m/z) and abundance of each ion

Question 33

molecules and mass spectrum

Answer 33

for molecules that are ionised by electron impact the signal with the greatest mass to charge value is from the molecular ion and its m/z value gives the relative molecular mass. however there may be some peaks presents around the molecular ion peak due to molecular ions that contain different isotopes.

Question 34

fragmentation and ions

Answer 34

when using electron impact there may be peaks with lower mass to value due to fragments caused by the break up of molecular ions

Question 35

what can mass spectrum do

Answer 35

mass spectrum can identify elements as they data is like a fingerprint etc.