Atomic Structure

Question 1

John Dalton

Answer 1

Thought atoms were spherical.
Different spheres constituted different elements.
Thought atoms were fundamental units of matter and were indivisible.

Question 2

J.J. Thompson

Answer 2

Discovered atoms were divisible.
Discovered and measured mass of electron.
Led to Plum Pudding Model (atom was a positively charged sphere with negatively charged electrons embedded in it)

Question 3

Ernest Rutherford

Answer 3

Fired alpha particles at a thin gold film.
Most particles passed straight through so disproved Plum Pudding Model.
Led to Nuclear Model (atom was mostly empty space with positive nucleus and orbiting electrons)

Question 4

Neils Bohr

Answer 4

Developed first quantum theory and discovered electron shells.
When electrons move between orbits, electromagnetic radiation of particular frequency must be emitted or absorbed

Question 5

Atomic Mass Unit (amu)

Answer 5

1/12 of mass of single carbon-12 atom

Question 6

Masses of subatomic particles

Answer 6

Proton = 1.0073 amu
Neutron = 1.0087 amu
Electron = 0.00055 amu

Question 7

Isotopes of hydrogen

Answer 7

Protium: one proton, one electron, no neutrons
Deuterium: one proton, one electron, one neutron
Tritium: one proton, one electron, two neutrons

Question 8

Relative isotopic mass

Answer 8

Average mass of a single isotope of an element divided by 1/12 of the mass of an atom of carbon-12

Question 9

Relative atomic mass

Answer 9

Average mass of a single atom of an element divided by 1/12 of the mass of an atom of carbon-12

Question 10

Relative molecular mass

Answer 10

Average mass of a molecule divided by 1/12 of the mass of an atom of carbon-12

Question 11

Time of flight mass spectrometer

Answer 11

Ionisation
Acceleration
Ion drift
Ion detection
Data analysis

Question 12

Ionisation

Answer 12

electrospray/ electron impact

Question 13

Acceleration

Answer 13

Electric field applied to give all ions same kinetic energy.

Heavier particles move slower.

Question 14

Ion drift

Answer 14

Ions deflected by magnetic field into a curved path.

Radius of their path is dependant on the charge and mass of the ion.

Question 15

Ion detection

Answer 15

Positive ions hit detection plate, gain electron producing flow of charge.
Greater abundance produces greater current.

Question 16

Data analysis

Answer 16

Analysed and recorded as mass spectra.

Question 17

Electrospray

Answer 17

Sample is dissolved in volatile, polar solvent
Injected through fine hypodermic needle giving fine mist or aerosol
Tip of needle has high voltage
At tip of needle sample molecule, M, gains a proton, H+ from solvent forming MH+
Solvent evaporates away while the MH+ ions move towards a negative plate
Peak with largest m/z value is equal to mass of MH+, have to subtract 1 to get Mr of molecule
Used for larger organic molecules, fragmentation does not occur

Question 18

Electron Impact

Answer 18

Vaporised sample is injected at low pressure
Electron gun fires high energy electrons at sample
Knocks out an outer electron
Forms positive ions with different charges
Used for molecules with low formula mass as fragmentation may occur with larger molecules

Question 19

Mass spectra for Cl2 and br2

Answer 19

Cl has two isotopes:
Cl35 (75%)
Cl37 (25%)
Br has two isotopes
Br79 (50%)
Br81 (50%)

Question 20

Use of mass spectrometers

Answer 20

Included in planetary space probes so elements on other planets can be identified as elements may have different composition of isotopes

Question 21

Electron configuration

Answer 21

Energy levels get closer together further from the nucleus.
Each orbital holds up to two electrons. Spin in opposite directions to minimise repulsion.
4s orbital fills before 3d. When d block elements form ions, lose 4s electrons first.

Question 22

degenerate

Answer 22

Orbitals with the exact same energy

Question 23

isoelectronic

Answer 23

Particles with same electron configuration

Question 24

electron configuration of copper

Answer 24

Cu = 1s22s22p63s23p64s13d10

Question 25

electron configuration of chromium

Answer 25

Cr = 1s22s22p63s23p64s13d5

Question 26

Simple ions

Answer 26

Name of positive ion is same as name of atom Na = sodium Na+ = sodium ion Name of negative ion is atom stem with -ide on the end Br = bromine Br- = bromide ion

Question 27

Shapes of orbitals

Answer 27

S subshells are spherical | P subshells are shaped like dumbbells

Question 28

First ionisation energy

Answer 28

Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 29

Second ionisation energy

Answer 29

Energy required to remove one mole of electrons from one mole of gaseous ions with a single positive charge to form one mole of gaseous 2+ ions

Question 30

Factors affecting ionisation energies

Answer 30

Atomic radius Nuclear charge Shielding Distance

Question 31

Atomic radius effect on ionisation energy

Answer 31

higher the atomic radius | lower the ionisation energy

Question 32

Nuclear charge effect on ionisation energy

Answer 32

greater number of protons greater nuclear charge higher ionisation energy

Question 33

Shielding effect on ionisation energy

Answer 33

more inner electrons causes more shielding lower ionisation energy

Question 34

Distance effect on ionisation energy

Answer 34

Electrons further away from nucleus easier to remove lower ionisation energy

Question 35

Trends down a group | ionisation energy

Answer 35

``` Outer electron further from nucleus, higher atomic radius Increased shielding due to more inner electrons Nuclear charge increases Ionisation energy decreases ```

Question 36

Trends across a period | ionisation energy

Answer 36

``` Electrons being added to same shell, atomic radius decreases Higher nuclear charge Same shielding Ionisation energy increases ```

Question 37

Group 3 first ionisation energies

Answer 37

``` Lower than expected first ionisation energy Have s2p1 arrangement outer p1 electron further from nucleus Inner s2 electrons increase shielding Less energy required ```

Question 38

Group 6 first ionisation energies

Answer 38

Lower than expected Have a p4 arrangement Repulsion of two electrons in same p orbital Less energy required

Question 39

Group 1 first ionisation energies

Answer 39

Lowest first ionisation energy in every period Greatest atomic radius Lowest nuclear charge

Question 40

Group 0 first ionisation energies

Answer 40

Highest first ionisation energy in every period Smallest atomic radius Highest nuclear charge

Question 41

Patterns in second ionisation energy

Answer 41

Patterns in first ionisation energy shifted one to the left | Group 1 elements would have highest second ionisation energy