Atomic structure

Question 1

mass number

Answer 1

protons and neutrons

Question 2

atomic number

Answer 2

protons

Question 3

isotopes

Answer 3

atoms of the same element with the same number of protons but diff number of neutrons.

Question 4

1803 John Dalton

Answer 4

atoms are spheres that could not be divided into any smaller parts

Question 5

1897 JJ Thompsomn

Answer 5

discovered electrons
atoms was a sphere of positive charge with negative electrons embedded in it

Question 6

1909 Ernest Rutherford

Answer 6

discovered the nucleus
nucleus was very small and positively charged
concluded that atoms was mostly empty space

Question 7

1913 Niels Bohr

Answer 7

discovered problem with Rutherford experiment
electrons orbit the nucleus at specific distance

Question 8

Describe the Experimental proof of Niels Bohr

Answer 8

when EM radiation is absorbed the electrons move between shells
they emit this radiation when electrons move down to lower energy levels

Question 9

define relative isotopic mass

Answer 9

the mass of an atom of an isotope compared
with 1/12 of the mass of an atom of carbon-12

Question 10

define relative atomic mass

Answer 10

the weighted mean / average mass of an atom of an
element compared with 1/12 of the mass of an atom of carbon-12

Question 11

define relative molecular mass

Answer 11

the weighted mean/ average mass of a molecule
compared with 1/12 of the mass of an atom of carbon-12

Question 12

define relative formula mass

Answer 12

the weighted mean mass of a formula unit
compared with 1/12 of the mass of an atom of carbon-12

Question 13

what are the four stages of mass spectrometer

Answer 13

ionisation
acceleration
ion drift/ flight tube
detection

Question 14

describe the process of ionisation: electron impact

Answer 14

-vaporised sample is injected at low pressure
-an electron gun fires high energy electrons at the sample
-knocks out an electron forming a +1 ion

Question 15

describe the process of ionisation:electron spray

Answer 15

• sample is dissolved in a volatile polar solvent
  -injected through a fine needle at high voltage
  -at the tip of the needle the sample molecule gains a proton
  -solvent then evaporates away while the + ions are attracted towards a negatively charged plate.

Question 16

describe the process of acceleration

Answer 16

-positive ions are accelerated by an electric field
accelerated to have the same KE
-+1 ions have the same KE so their velocity depends on their mass

Question 17

what does the velocity of a particle depend on

Answer 17

its mass and so lightest particle move faster than the heaviest particle

Question 18

describe the process of ion drift

Answer 18

positive ions enter the flight tube
particles will move at diff velocity depending on their mass
velocity at which an ions moves will determine its time of flight ( time it takes for particles to move through the tube)

t=d/v and KE=1/2mv^2

t=d square root of m/2KE

Question 19

describe the process of detection

Answer 19

once passed through the mass spectrometer the +1 ions will hit a negatively charged detector plate

as they hit the detector plate they gain an electron

gaining of the electron discharges the ion and causes a current to be produced

This size of the current is proportional to the abundance of those ions hitting the plate and gaining an electron

The detector plate is connected to a computer, which produces the mass spectrum

Question 20

define ionisation

Answer 20

• minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in gaseous state

Question 21

describe the effect on shielding

Answer 21

• the more electron shells between the positive nucleus and the negative electron that is being removed, the less energy required.
  -there is a weaker attraction

Question 22

describe the effect on nuclear charge

Answer 22

-the more protons in the nucleus, the greater the attraction between the nucleus and outer electron
- this means more energy required to remove the electron

Question 23

describe the effect on atomic size

Answer 23

the bigger the atom, the further away the outer electrons are from the nucleus
less attractive forces between nucleus and outer electron so easier to remove

Question 24

electron configuration of cr

Answer 24

1s2 2s2 2p6 3s2 3p6 3d5 4s1

Question 25

define successive ionisation

Answer 25

-the removal of more than 1 electron from the same atom

Question 26

why does ionisation energy decrease as we go down a group?

Answer 26

-the atomic radius increases as we go down the group because the outer electron is further away from the nucleus. weaker attraction forces . less energy required to remove electron

-Shielding increases . More shells between the nucleus and the outer shell. attractive forces are weaker . less energy needed to remove the electron.

Question 27

why does ionisation energy increase as we move across a period

Answer 27

-increasing number of protons in the nucleus . increases the nuclear attraction

-shielding is similar and distance from the nucleus marginally decreases,

• more energy is required to remove an outer electron.

Question 28

Explain why the first ionisation energy of Al is less than that of Mg?

Answer 28

the outer electron of Al is removed from the 3p subshell whereas the outer electron in Mg is removed from the 3s subshell

the 3p subshell in in higher energy level than the 3s subshell

-aluminiums outer electron is further away from the nucleus and so weak attraction.-
less energy needed to remove outer electron in Al

Question 29

Explain why the first ionisation energy of sulfur is different from that of phosphorus.

Answer 29

sulphur: 1s2 2s2 2p6 3s2 3p4
phosphorus: 1s2 2s2 2p6 3s2 3p3

In the 3p orbital of sulphur, the electrons are paired
In the 3p orbital of phosphorus, it contains a lone electron

paired electron in sulphur causes an electron repulsion so less energy is needed to remove an electron from an orbital of 2 in than 1 like Phosphorous