the structure of atoms

Question 1

what is the mass of a proton?

Answer 1

1

Question 2

the charge of a proton?

Answer 2

+1

Question 3

what is the mass of a neutron?

Answer 3

1

Question 4

what is the charge of a neutron ?

Answer 4

0

Question 5

what is the mass of an electron ?

Answer 5

negligible

Question 6

what is the charge of an electron ?

Answer 6

-1

Question 7

what is meant by the relative atomic mass (Ar) ?

Answer 7

the mass of an atom relative to the 12C isotope with value of 12

Question 8

what is the calculation for Ar

Answer 8

average mass per atom of an element / mass of one atom of Carbon-12 x12

Question 9

what is meant by mass spectroscopy ?

Answer 9

mass spectroscopy is an instrumental technique used to find the relative mass of elements and compounds

Question 10

what occurs in electrospray ionisation ?

Answer 10

• the element is dissolved in a volatile solvent.
• the dissolved solvent is then forced into a very thin needle and is then sprayed
• the end of the needle is then put through a very high voltage which forces the solvent to gain a H+ proton which therefore makes it become a positive ion

Question 11

what is meant by a volatile solvent ?

Answer 11

a volatile solvent makes the element turn into a gas very easily

Question 12

what happens during the electric field in the time of flight spectrometer ?

Answer 12

• the ions are all accelerated by an electric field so that all of the ions have the same kinetic energy at a specific point
  -its calculated using : kinetic energy = 0.5 x mass x velocity ^2

Question 13

what happens in the flight tube in the ToF mass spectrometer ?

Answer 13

-the ions enter the flight tube
- because the ions have different isotopes, they all have different masses and times of flight
- lighter ions = shorter time of flight
heavier ions = longer time of flight

Question 14

what is the term used when ions enter the flight tube ?

Answer 14

ion drift

Question 15

what is the detector ?

Answer 15

a negatively charged plate

Question 16

what happens when the ions hit the plate ?

Answer 16

when ions hit the plate a current is produced
- so the more ions that hit the detector the bigger the current

Question 17

how are we able to calculate the abundance (number of particles ) of the particles ?

Answer 17

because the size of the current is directly proportional to the number of ions hitting the plate

Question 18

how can we calculate the mass of ions hitting the detector ?

Answer 18

from the time it takes to reach the detector

Question 19

what is the equation for electrospray ionisation ?

Answer 19

element X (g) + H+ —> XH+ (g)

Question 20

electron gun ionisation method ?

Answer 20

• element sample is vapourised into a gas
• it passes through the machine and an electron gun bombards high energy electrons at the sample
• this forces the element to lose an electron as it knocks it off
  therefore forming a +1 ion

Question 21

what is the equation for electron gun ionisation ?

Answer 21

element X(g) —-> X+ (g) positive ion + e-
- as it loses an electron

Question 22

relative atomic mass of isotopes equation ?

Answer 22

Ar = total mass of all isotopes / total abundance