atomic structure

Question 1

What are the three sub atomic particles ?

Answer 1

• protons, neutrons and electrons

Question 2

Explain the general electron configuration of atoms

Answer 2

• energy level surround the nucleus
• these energy level have sub shells
• the sub shells contain orbitals which can hold up to two electrons of opposite spins
• sub shells are filled up in order of increasing energy

Question 3

What are the 4 types of sub shells ?

Answer 3

• s = 1 orbital, 2 electrons
• p = 3 orbitals, 6 electrons
• d = 5 orbitals , 10 electrons
• f = 7 orbitals, 14 electrons

Question 4

What about the 3d sub shell is unique ?

Answer 4

• it has more energy than the 4s sub shell and so is written after in electron configurations

Question 5

What is different about the electron configurations of chromium and copper

Answer 5

• the second electron in the 4s sub shell goes to the 3d sub shell so that its 3d5 for chromium and 3d10 for copper
• this helps them be more stable

Question 6

What is the definition of relative atomic mass ?

Answer 6

• the weighted average mass of an atom of an element compared to 1/12 the mass of a carbon atom-12 atom

Question 7

What is the definition of relative molecular mass ?

Answer 7

• the average mass of a molecule compared to 1/12 the mass of a carbon-12 atom

Question 8

What is are isotopes?

Answer 8

• atoms of the same element that have the same number of protons but different number of neutrons so therefore different mass numbers

Question 9

What is the definition of relative isotopic mass ?

Answer 9

• the mass of an atom of an isotope compared to 1/12 the mass f a carbon-12 atom

Question 10

How are the chemical properties of different isotopes ?

Answer 10

• they are the same
• because they have the same electron configuration

Question 11

How are the physical properties of different isotopes ?

Answer 11

• they are slightly different to each other
• because physical properties depend on atomic mass

Question 12

What are mass spectrometers used for ?

Answer 12

• to determine the relative atomic mass based on the abundance and mass of each isotope in a sample
• it is an analytical technique

Question 13

What are the 4 stages of a mass spectrometer ?

Answer 13

• ionisation, acceleration, ion drift and detection

Question 14

What are the two types of ionisation methods ?

Answer 14

• electron impact and electrospray ionisation

Question 15

How does electron impact work ?

Answer 15

• the sample is vaporised then bombared with high energy electrons
• these high energy electrons come from a hot filament wire as it emits electrons as a current runs through it
• this is the ‘electron gun’
• an electron is knocked off forming a 1+ ion

Question 16

How does electro spray ionisation work ?

Answer 16

• the sample is dissolve into a volatile solvent
• then the solvent is injected into the mass spectrometer using a hypodermic needle so it produces a fine mist/aerosol
• the needle is attaches to a high voltage power supply so that when the samples is injected the particles gain a proton ( H+ ) from the solvent
• to form a 1+ ion

Question 17

What happens during the acceleration stage of mass spectrometry ?

Answer 17

• the positive ions are attracted to a negatively charged plate by an electric field
• so now they have identical kinetic energy
• but because some ions are bigger than others , the lighter ions will move faster

Question 18

What happens in the ion drift stage of mass spectrometry ?

Answer 18

• the ions enter a flight tube where they just drift
• lighter ions have higher velocities and so reach the detector quicker than the heavier ions

Question 19

What happens in the detection stage of mass spectrometry ?

Answer 19

• the ions hit the detector and gain an electron
• the movement of electron creates an electric current
• the size of the current is proportional to the abundance of the isotope

Question 20

When is it appropriate to use the electron impact technique ?

Answer 20

• when the substances have a lower molecular mass

Question 21

When is is it appropriate to use the electro spray ionisation technique ?

Answer 21

• when the substances have a higher molecular mass

Question 22

What is the shape of an s subshell ?

Answer 22

• spherical

Question 23

What is the shape of the p subshell ?

Answer 23

• a dumbbell shape

Question 24

What is the definition of first ionisation energy

Answer 24

• the amount of energy / enthalpy change needed to remove 1 mole of electrons from 1 mole of gaeosus atoms to form 1 mole of uni-positive gaseous ions

Question 25

What is the definition of second ionisation energy ?

Answer 25

- the energy needed / enthalpy change when 1 mole of electrons is removes from 1 mole of uni-positive gaseous ions to form 1 mole of gaseous 2+ ions

Question 26

What are the factors that affect ionisation energy ?

Answer 26

- nuclear charge = higher charge means greater attraction so more energy needed to remove electrons - atomic radius = larger radius means less attraction so less energy needed - shielding = more shielding means less energy needed because outer shell electrons are repelled by inner shell electrons

Question 27

Why are successive ionisation energies generally increasing ?

Answer 27

- because when the first electron is removed, a positive ion is formed - meaning there is more protons than electrons - so the remaining attraction on all the electrons is increased - making it harder to remove one

Question 28

What group is an element in if there is a jump in ionisation energy between the 4th and 5th electron ?

Answer 28

- group 4 - because the 5th electron in an inner shell closer to the nucleus - and has no/less shielding - so experiences a stronger attraction from the nucleus

Question 29

Describe the trend in first ionisation energies across period 3 ?

Answer 29

- the general trend is that it increases - because the amount of protons is increasing asking the attraction from the nucleus greater ( shielding and atomic radius have no effect ) - between magnesium and aluminum there is a slight drop - because aluminium is beginning to fill up the 3p subshell whilst magnesium ends in 3s - and he 3p electron have higher energy and are slightly shelided by 3s electrons so are easier to remove - there is also a drop between phosphorus and sulphur - because phosphorus has 3 electron is the 3p subshell whilst sulphur has 4 electron in the 3p subshell and the 4th one begins to double fill the first 3p orbital. - the repulsion between the 2 electrons makes the second electron easier to remove

Question 30

What is the trend in first ionisation energies down group 2 ?

Answer 30

- as you go down the group, first ionisation energy decreases - as outermost electron are held successively further from the nucleus in additional shells - and there is more shielding - so the attraction of the nucleus becomes smaller

Question 31

Why does helium have the largest first ionisation energy ?

Answer 31

- it’s first electron is in the first shell closest to the nucleus - and there are no shielding effects from near shells - helium has a bigger ionisation energy than hydrogen because is has one more proton