3.1.1 atomic structure

Question 1

what does the mass number represent?

Answer 1

the number of protons and neutrons

Question 2

why may atoms of the same element have different mass numbers?

Answer 2

they may have isotopes since they have a different number of neutrons

Question 3

what is a mass spectrometer used for?

Answer 3

• calculate relative atomic mass
• calculate relative molecular mass

Question 4

what else can a mass spectrometer help determine aside from ar and mr?

Answer 4

relative isotopic mass and relative abundance of isotopes

Question 5

what are the principles of a simple time of flight mass spectrometer?

Answer 5

1. ionisation
2. acceleration
3. drift region
4. detection

Question 6

explain the 2 types of ionisation

Answer 6

electron impact - sample is bombarded with high energy electrons to knock off an electron
electrospray ionisation - sample dissolved in a volatile solvent and injected through a needle to give an aerosol occurs via the gain of a proton

Question 7

why must the sample be ionised?

Answer 7

only ions will interact with the electric field and create a current

Question 8

explain how acceleration works

Answer 8

positive ions are accelerated by an electric field so that all ions have the same kinetic energy

Question 9

explain what the drift region is

Answer 9

positive ions pass through a hole in a negatively charged plate
their time of flight depends on their velocity

Question 10

explain what detection is

Answer 10

positive ions hit a negative plate and a re discharged by gaining and electron
movement if electrons generates an electric current

Question 11

what have equation to calculate Ar?

Answer 11

sum of (mass of isotope x relative abundance) / sum of abundances

Question 12

what are the sub shells?

Answer 12

s subshell
p subshell
d subshell
f subshell

Question 13

what is an orbital?

Answer 13

a 3D region of space where there is a 95% probability of finding an electron
they can hold a maximum of 2 electrons of opposite spin

Question 14

how many orbitals are each of the subshell made up of?

Answer 14

s subshell : 1 orbital ( 2 electrons)
p subshell : 3 orbitals ( 6 electrons )
d subshell : 5 orbitals (10 electrons)
f subshell: 7 orbitals (14 electrons)

Question 15

what is the aufbau principle?

Answer 15

electrons will fill the lowest energy subshell first and will not fill another until that one is full

Question 16

what is Hunds Rule?

Answer 16

electrons will occupy their own orbitals before sharing

Question 17

define first ionisation energy

Answer 17

the energy required to remove one electron from each atom in one mole of gaseous atoms

Question 18

write an equation for the first ionisation energy

Answer 18

X(g) — X+(g) + e-

Question 19

what factors affect ionisation energy?

Answer 19

1. atomic radius
2. nuclear charge
3. shielding effect

Question 20

explain the effect atomic radius has on ionisation energy

Answer 20

the higher the energy of the electron subshell, the further away it’s from the nucleus and the weaker the attraction between the nucleus and the outer electron

Question 21

explain the effect nuclear charge has on ionisation energy

Answer 21

the higher the nuclear charge the stronger the attraction between the nucleus and outer electron

Question 22

explain the effect shielding has on ionisation energy

Answer 22

the greater the number of electron shells the greater the shielding effect causing a weaker attraction between the nucleus and the outer electron

Question 23

what are successive ionisation energies?

Answer 23

sequential removal of an electron from an atom to form an increasingly positive ion

Question 24

what is the trend for ionisation energies down a group

Answer 24

ionisation energy decreases