Atomic structure

Question 1

Relative atomic mass

Answer 1

the weighted mean of the mass of an elements atoms
to 1/12 the mass of carbon-12

Question 2

Relative isotopic mass

Answer 2

the mass of an atom of an isotope
relative to 1/12 the mass of carbon-12

Question 3

1st stage of mass spectrometry

Answer 3

ionisation
- particles are ionised via bombardment with high energy electrons
- generates positive ions

Question 4

2nd stage of mass spectrometry

Answer 4

ions are accelerated by an electric field

Question 5

3rd stage of mass spectrometry

Answer 5

deflection
- ions pass through strong magnetic fields
- lighter ions are deflected more

Question 6

4th stage of mass spectrometry

Answer 6

detection
- ions are detected electronically as currents
- size of current indicates abundance

Question 7

How is the mass of an isotope detected using time of flight

Answer 7

• all ions are accelerated so they have equal kinetic energy
  KE = 1/2MV2
• ions with different velocities will have different masses
• velocity can be calculated using time and distance

Question 8

What is the first ionisation energy definition

Answer 8

the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 9

Equation for 1st ionisation energy

Answer 9

X(g) -> X+(g) + e-

Question 10

Factors that affect ionisation energies

Answer 10

• nuclear charge
• distance of outer electrons from nucleus
• shielding

Question 11

What is the trend in ionisation energies across a period

Answer 11

increases
- greater nuclear charge so greater attraction between electrons and nucleus

Question 12

What is the trend in ionisation energies down a group

Answer 12

decreases
- more shells so shielding and distance between nucleus and electrons increases

Question 13

How many electrons does each quantum shell hold

Answer 13

1st - 2
2nd - 8
3rd - 18

Question 14

What shape are s orbitals

Answer 14

spherical

Question 15

What shape are p orbitals

Answer 15

dumbbell shaped

Question 16

What is an orbital

Answer 16

an area in space that has a 95% chance of finding an electron

Question 17

Explain why the 1st ionisation energy of group 2 is less than that of a group 3

Answer 17

the outermost electron from a group 2 is removed from an s subshell rather than a p subshell which is closer to the nucleus

Question 18

Explain why the 1st ionisation energy decreases from phosphorus to sulfur

Answer 18

in sulfur the p electros are paired for the first time
- repulsions are set up between paired electrons
- this reduces energy needed to remove the electron

Question 19

Which groups are in the s block

Answer 19

groups 1 + 2

Question 20

Which groups are in the p block

Answer 20

groups 3 - 8

Question 21

Which groups are in the d block

Answer 21

transition metals

Question 22

How can you identify the group of an element from ionisation energies

Answer 22

big jumps in ionisation energies indicate that an electron is being removed from a subshell closer to the nucleus
group 1 - jump between IE 1 and IE 2

Question 23

What is periodicity

Answer 23

chemical trends that repeat across periods

Question 24

Which properties show periodicity

Answer 24

• melting and boiling points
• atomic radius

Question 25

Why does melting and boiling points increase from group 1 - 3

Answer 25

metals which bond metallically
group 1 - 1e- per atom delocalised
group 2 - 2e- delocalised

results in stronger attraction between delocalised electrons and + ions
- requires more energy to overcome

Question 26

Why are melting and boiling points the highest in group 4

Answer 26

form giant covalent structures
- strong covalent bonds between atoms

Question 27

Why does melting and boiling points decrease in group 5 - 7

Answer 27

simple molecular substances with weak intermolecular forces

Question 28

Why is there a slight increase in the melting and boiling points of phosphorus and sulfur

Answer 28

phosphorus tends to be p4
sulfur is s8

Question 29

What is atomic radius

Answer 29

distance from the centre of nucleus to the boundary of the electron cloud
- difficult to determine

Question 30

What are the two ways to find atomic radius

Answer 30

• covalent radius
• van der waal’s radius (two atoms touching eachother rather than overlapping)

Question 31

Why does atomic radius decrease along a period

Answer 31

nuclear charge increase so greater attraction to electrons, so the electron cloud is pulled in tighter
- attraction to nuclear far outweighs repulsions between electrons

Question 32

Why does atomic radius increase down a group

Answer 32

more shells