atomic structure

Question 1

what is an isotope

Answer 1

isotopes are atoms of the same element that contain the same number of protons and electrons but a different number of neutrons

Question 2

how can you calculate the RAM of an atom using the average mass of isotopes

Answer 2

(isotope 1 abundance x mass) + (isotope 2 abundance x mass) divided by 100

Question 3

what are the units of mass, velocity, time and length of tube in time of spec calculations

Answer 3

mass - kg
velocity- ms^-1
time- seconds
length- metres

Question 4

what are the 4 steps on mass spectrometry

Answer 4

ionisation, acceleration, ion drift adn detection

Question 5

what are the two types of ionisation in mass spec

Answer 5

electron impact and electrospray ionisation

Question 6

how does electron impact ionisation work

Answer 6

1. The sample is vapourised and then bombarded with high energy electrons which are fired from an electron gun forming 1+ ions.

Question 7

how does electrospray ionisation work

Answer 7

1. The sample is dissolved in a volatile solvent
2. the solvent is injected into the mass spec using a hypodermic needle and the needle is attatched to a high voltage power supply so as the sample is injected the particles are ionised by gaining a proton from the solvent
3. The solvent evaporated

Question 8

when is electron impact and electrospray ionisation used

Answer 8

electron impact is used for elements and substances which have a lower molecular mass

electrospray ionisation is used for substances with a higher molecular mass

Question 9

what happens in acceleration

Answer 9

the ions formed from ionisaiton are accelerated using an electric field and they are accelerated to all have the same kinetic energy

Question 10

what happens in ion drift

Answer 10

the ions will pass through a hole in the negatively charged plate and into the flight tube

Question 11

what happens in detection

Answer 11

the ions hit a negatively charged detector plate and they gain an electron again which causes the ion to be discharged and causes a current to be produced

Question 12

why is the current important in mass spec

Answer 12

the size of the current is proportional to the abundance of those ions hitting the plate

Question 13

how many orbitals are in s, p, d and f

Answer 13

s-1
p-3
d-5
f-7

Question 14

what is the exception in orbitals filling and what 2 elements ddont follow it

Answer 14

4s fills before 3d as it has a slightly lower energy
chromium and copper

Question 15

what four factors is ionisation energies effected by

Answer 15

strength of nuclear charge
the atomic radius
shielding
spin pair repulsion

Question 16

what is ionisation energy

Answer 16

the ionsation energy is the amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to from one mole of gaseous ions

Question 17

what is the first ionisation energy

Answer 17

the first ionisation energy is the energy required to remove one mole of electrons from one mole of atoms of an element to from one mole of 1+ ions

Question 18

what is the trend of ionisation energy across a period and why

Answer 18

increases

the nuclear charge increases but the amount of shells and shielding stays the same so the atomic radius is decreased slightly due to stronger electrostatic attraction between valence electrons and the nucleus so it becomes harder to remove an electron the higher the nuclear charge

Question 19

what are the exceptions to the trend across a period in ionisation energy

Answer 19

between boron and beryllium as the fifth electron is in the 2p subshell which is further away then the 2s subshell of beryllium before

decrease between nitrogen adn oxygen due to spin pair repulstion in the 2p orbital

Question 20

what is the trend in ionisation energy down a group

Answer 20

decreases

the electron shielding and larger atomic radius outweigh the increasing nuclear charge so it becomes easier to remove an electron so it takes less energy