3.1 Physical Chemistry: .1 Atomic Structure

Question 1

what did Robert Boyle propose? and state the time that this theory came to be.

Answer 1

• boyle proposed that there were some substances that could not be made simple. These were chemical elements as we know them.
• 1661

Question 2

what did Greek philosophers believe when it came to the make up of everything on the earth?

Answer 2

-matter was made up of a single continuous substance that produced the four elemetns- earth, fire, water and air

Question 3

what did John Dalton propose? and state the time that this theory came to be.

Answer 3

• dalton described atoms as solid spheres (indivisible)
• he also said that different spheres make up different elements

Question 4

what did JJ Thompson propose? and state the time that this theory came to be.

Answer 4

-JJ discovered the electron. he showed that electrons were negatively charged (through his plum pudding model) and electrons from all elements were the same.

Question 5

what did Henry Becquerel propose? and state the time that this theory came to be.

Answer 5

• henri discovered radioactivity which showed that particles could come from inside an atom
• 1896

Question 6

what did Earnest Rutherford propose? and state the time that this theory came to be.

Answer 6

• Rutherford and his team conducted the famous gold foil experiment (they fired positively charged alpha particles at a very thin sheet of gold).
• plum pudding suggested that most alpha particle would be slightly deflected by the positive part of the atom but actually most passed through with a small number being delflected back.
• so rutherford developed the nuclear model of the atom which had a tiny positively charged nuclues surrounded by a cloud of negative electrons

Question 7

what did Niels Bohr propose? and state the time that this theory came to be.

Answer 7

• scientists quickly realised that electrons in a cloud would quickly around the nucleus of an atom would quickly spiral down into the nucleus causing the atom to collaps
• bohr proposed a new model where the atoms exist in shells or orbits of fixed energy

Question 8

how was Bohr’s model refined?

Answer 8

scientist later discovered that not all electrons in a shell have the same energy which meant Bohr’s model was not quite right so they refined it to include sub shells

Question 9

on a periodic table what does the top number (the relative atomic mass tell you?

Answer 9

-the amount of protons and neutrons in a atom

Question 10

on a periodic table what does the bottom number (the atomic number) tell you?

Answer 10

the number of protons (also electrons as the number of protons are equal to the number of protons)

Question 11

what is the atom made up of?

Answer 11

proton, electrons and neutrons

Question 12

for each particle state the mass and the charge: proton neutron and electron

Answer 12

proton: mass=1 charge= +1 electron: mass= 1/1840 charge= -1 neutron: mass=1 charge=0

Question 13

what forces can be found in a atom?

Answer 13

-strong nuclear force: this force holds together the protons and neutrons in the centre of the atom -electrostatic force: this force holds protons and electrons together in the atom, it is less strong than the nuclear force

Question 14

what is the equation for relative atomic mass

Answer 14

Ar= average mass of 1 atom/ (1/12) mass of 1 atom of carbon 12

Question 15

what is the equation for the relative molecular mass

Answer 15

Mr= average mass of the molecule/ (1/2) mass of 1 atom of carbon 12

Question 16

what are isotopes?

Answer 16

isotopes have the same atomic number but different mass numbers they have the same number of protons and same number of electrons but different number of neutrons

Question 17

why are isotopes chemically identical?

Answer 17

they are chemically identical because they have the same number of electrons

Question 18

why do isotopes have different physical properties?

Answer 18

they have different physical properties because they have different masses e.g Cl (35) has a higher mass, higher density higher melting and boiling point slower rate of diffusion

Question 19

what is does mass spectrometry help you to determine?

Answer 19

the relative atomic mass

Question 20

what are the stages inv mass spectrometry?

Answer 20

vaporisation, ionisation, acceleration, separation and detection

Question 21

what happens in the normal type of mass spectrometry?

Answer 21

-the sample is injected in and vaporised in a gaseous atom -the sample is ionised by high energy electrons shot from the electron gun. ionisation must occur for the next stages M(g) —> Mg+ + e- -a pair of parallel plates plates generate and electric field which forms a column for fast moving electrons. The first plate is positive with respect to the second plate -in the separation stage ions are separated depending on the mass to charge ratio (m/z). Ions with a smaller mass to charge ratio are deflected more easily and hit the detector however increasing the magnetic field allows ions with a greater m/z values to hit the detector. -in the detection stage when ions hit the detector, a current is produced which causes a pen deflection and a peak is drawn on the spectrum

Question 22

what happens in a TOF mass spectrometer

Answer 22

-the whole apparatus is kept under a high vacuum to prevent the ions that are produced colliding with molecules from the air -the is sample dissolved in a volatile solvent which is passed through an inlet valve, this is connected to the positive terminal of aa high voltage supply. the sample is ionised at a voltage of 3-4kV producing positively charged droplets. The solvent evaporates from the droplets, the droplets get smaller and smaller until they are a single positively charged ion. M(g) —> Mg+ + e- -the ions are attracted by a negatively charged plate, they gain kinetic as they are accelerating towards the negatively charged plate. As Ke= 1/2mv^2 those particles with a higher mass to charge ratio will move with a lower velocity (smaller ions move with a higher speed, larger ions move with a lower speed) -in the drift region is a high vacuum region. The electrons pass through forming a beam and travel along a tube, called the flight tube to the detector. The ions enter the drift region with different speeds hence they will be separated in the drift region as smaller ions will have a shorter time of flight and reach the detector first -the flight times of the ions are recorded and the positive ions pick up an electron from the detector which causes a current to flow.

Question 23

how has the TOF spectrometer been improved?

Answer 23

the vaporisation, ionisation and acceleration has been combined -as the sample dissolved in solvent leaves the end of the capillary, the sample is ionised as a voltage of 3-4kV is applied to the end of the capillary -the droplet leaving the capillary is full of ions, the solvent evaporates and a spray of gaseous ions is produced -ions are attracted by the extraction electrode. all the ions gain the same kinetic energy and enter the drift region -the drift region is a high vacuum region where no electric fields are present.

Question 24

how is a current generated in the mass spectrometer?

Answer 24

the ion hits the detector and gains an eleton which allows a current to flow

the current is amplified and the peak is created

Question 25

how can you calculate the relative atomic mass of an element?

Answer 25

relative atomic mass= (abundance x mass to charge ratio) + (abundance x mass to charge ratio)…./100

Question 26

what can a mass spectrometer be used for?

Answer 26

-space probes such as the mars rover use mass spectrometer. they use is it to identify elements in rock samples -crime officers looking for rugs, explosives or chemical weapons or investigating chemical spills

Question 27

what is the formula for Sulphuric acid? and which are the ions involved?

Answer 27

H2SO4: H^2+ SO4^2-

Question 28

what is the first ionisation energy? and give the equation

Answer 28

the heat energy required to remove one mole of an electron from one gaseous atoms to form one mole of gaseous positive ions K(g) —> K+(g) + e-

Question 29

what are the standard conditions for first ionisation energy?

Answer 29

2.98 K + 100Pa

Question 30

what is second ionisation energy? and give the equation

Answer 30

the heat energy required to remove one mole electron form a uni positive gaseous ion to form a di positive gaseous atom. k+ —-> K2+ + e-

Question 31

is it easier or harder to remove a second electron? why?

Answer 31

harder, because an electron is being removed from a positive charged ions

Question 32

*on a graph or on a table what does a large difference in ionisation energy indicate?

Answer 32

a change in main energy level

Question 33

in electron arrangement what is the relationship between the distance from the nucleus and the energy level?

Answer 33

the further away from the nucleus the higher the energy level

Question 34

for each sub level: s,p,d,f how many electrons can it hold and how many orbitals are there?

Answer 34

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

Question 35

what subshells are the main energy levels split into

Answer 35

1: 1s 2: 2s 2p 3: 3s 3p 3d 4. 4s 4p 4d 4f

Question 36

what is the electron configuration for iron?

Answer 36

1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^6, 4s^1 or [Ar] 3d^6, 4s^2

Question 37

what is the electron configuration for copper and why is it like this?

Answer 37

[Ar] 3d^9 4s^2 the [Ar] 3d^10, 4s^1 this is because in the 4s2 electrons unpair to go fill up the 3d sublevel

Question 38

what does isotonic mean?

Answer 38

has the same number of electrons

Question 39

give the ion arrangement for sodium and state which element it is isotonic with

Answer 39

Na -1s^2 2s^2 2p^6 3s^1 Na+- 1s^2 2s^2 2p^6 isotonic with Neon

Question 40

why is there a general increase in the first ionisation energy across a period?

Answer 40

because the number of protons in the nucleus increases across a period so there is a stronger electrostatic force between the positive protons and negative electrons. This makes it harder to remove the electron on the highest sub level.

Question 41

why would there be a large drop in ionisation energy between Helium and Lithium?

Answer 41

because Lithium has one more main energy level that helium. This means that the electron that will be removed is more further away and shielded from the nucleus. This means it take less energy to overcome the attraction of the protons in the nucleus.

Question 42

why would there be a slight drop in ionisation energy between Beryllium and Boron

Answer 42

even though there are more protons in the Boron, the 2p^1 electron (outer electron) is the on a higher sub energy level than that of Beryllium (2s^2) and therefor Boron requires less energy to remove the electron than Beryllium

Question 43

on the graph between from Boron to Nitrogen, why is there a slight increase in ionisation energy?

Answer 43

There is similar shielding as electrons occupy the same energy level so this is not a factor. It is because of the number of protons in the nucleus increasing which means that the electrostatic force between the protons and electrons get stronger therefore more ionisation energy is required to remove the electron

Question 44

why would there be a slight dip in the ionisation energy between nitrogen and oxygen?

Answer 44

Oxygen’s outer electron is 2p^3 whilst Nitrogen is 2p^4. this shows that in nitrogen the 4th electron is sharing an orbital. This causes a repulsion so the electrons have to have an opposite spin. Because of this repulsion, less energy is required to remove the electron despite the nuclear charge, hence the drop in ionisation energy.

Question 45

what is the trend in ionisation energy going down a group and why?

Answer 45

It decreases, This is because the outer electron is a main level that gets further away from the nucleus. Therefore the electron is less shielded from the attraction from the nucleus and requires less energy to be removed, hence the decrease in ionisation energy. (the nuclear charge does increase but is overcome by the effect of the inner electrons shielding the nuclear charge)

Question 46

what is the formula for nitric acid and which are the ions involved?

Answer 46

HNO3: H+ NO3^-

Question 47

what is the formula for carbonic and which are the ions involved?

Answer 47

H2CO3: H^2+ CO3^2-

Question 48

what is the formula for Phosphoric acid and which are the ions involved?

Answer 48

H3PO4: H^3+ PO4^3-

Question 49

what is the formula for sodium hydroxide and which ions are involved?

Answer 49

NaOH: Na+ OH-

Question 50

what is the formula for Ammonium and which ions are involved?

Answer 50

NH4OH: NH4+ OH-

Question 51

Questions: from knowing the formulas of acids and ions involved work out the ions in these chemicals: 1. magnesium chloride: Mg2CL 2. magnesium sulphate: Mg2SO4 3.Magnesium Nitrate= Mg3 NO3 4.Magnesium Carbonate= Mg2CO3 5.Magnesium Phosphate 6. Magnesium /hydroxide

Answer 51

1. Mg2+ Cl- so MgCl2 2.Mg2+ SO4^2- MgSO4 3.Mg2+ NO3- Mg (NO3)2 4.Mg2+ CO3^2- MgCO3 5.Mg2+ PO4^3- Mg3 (PO4)2

Question 52

what is the formula for hydrochloric acid? and which are the ions involved?

Answer 52

HCl: H+ Cl-

Question 53

what does it mean to have a noble gas electron arrangement

Answer 53

the chemical has a full outer shell of electrons