3.1 Physical Chemistry: .1 Atomic Structure Flashcards
what did Robert Boyle propose? and state the time that this theory came to be.
- boyle proposed that there were some substances that could not be made simple. These were chemical elements as we know them.
- 1661
what did Greek philosophers believe when it came to the make up of everything on the earth?
-matter was made up of a single continuous substance that produced the four elemetns- earth, fire, water and air
what did John Dalton propose? and state the time that this theory came to be.
- dalton described atoms as solid spheres (indivisible)
- he also said that different spheres make up different elements
what did JJ Thompson propose? and state the time that this theory came to be.
-JJ discovered the electron. he showed that electrons were negatively charged (through his plum pudding model) and electrons from all elements were the same.
what did Henry Becquerel propose? and state the time that this theory came to be.
- henri discovered radioactivity which showed that particles could come from inside an atom
- 1896
what did Earnest Rutherford propose? and state the time that this theory came to be.
- 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
what did Niels Bohr propose? and state the time that this theory came to be.
- 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
how was Bohr’s model refined?
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
on a periodic table what does the top number (the relative atomic mass tell you?
-the amount of protons and neutrons in a atom
on a periodic table what does the bottom number (the atomic number) tell you?
the number of protons (also electrons as the number of protons are equal to the number of protons)
what is the atom made up of?
proton, electrons and neutrons
for each particle state the mass and the charge: proton neutron and electron
proton: mass=1 charge= +1 electron: mass= 1/1840 charge= -1 neutron: mass=1 charge=0
what forces can be found in a atom?
-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
what is the equation for relative atomic mass
Ar= average mass of 1 atom/ (1/12) mass of 1 atom of carbon 12
what is the equation for the relative molecular mass
Mr= average mass of the molecule/ (1/2) mass of 1 atom of carbon 12
what are isotopes?
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
why are isotopes chemically identical?
they are chemically identical because they have the same number of electrons
why do isotopes have different physical properties?
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
what is does mass spectrometry help you to determine?
the relative atomic mass
what are the stages inv mass spectrometry?
vaporisation, ionisation, acceleration, separation and detection
what happens in the normal type of mass spectrometry?
-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
what happens in a TOF mass spectrometer
-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.
how has the TOF spectrometer been improved?
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.
how is a current generated in the mass spectrometer?
the ion hits the detector and gains an eleton which allows a current to flow
the current is amplified and the peak is created
how can you calculate the relative atomic mass of an element?
relative atomic mass= (abundance x mass to charge ratio) + (abundance x mass to charge ratio)…./100
what can a mass spectrometer be used for?
-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
what is the formula for Sulphuric acid? and which are the ions involved?
H2SO4: H^2+ SO4^2-
what is the first ionisation energy? and give the equation
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-
what are the standard conditions for first ionisation energy?
2.98 K + 100Pa
what is second ionisation energy? and give the equation
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-
is it easier or harder to remove a second electron? why?
harder, because an electron is being removed from a positive charged ions
*on a graph or on a table what does a large difference in ionisation energy indicate?
a change in main energy level
in electron arrangement what is the relationship between the distance from the nucleus and the energy level?
the further away from the nucleus the higher the energy level
for each sub level: s,p,d,f how many electrons can it hold and how many orbitals are there?
s= 2 electrons 1 orbital p= 6 electrons 3 orbitals d= 10 electrons 5 orbitals f= 14 electrons 7 orbitals
what subshells are the main energy levels split into
1: 1s 2: 2s 2p 3: 3s 3p 3d 4. 4s 4p 4d 4f
what is the electron configuration for iron?
1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^6, 4s^1 or [Ar] 3d^6, 4s^2
what is the electron configuration for copper and why is it like this?
[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
what does isotonic mean?
has the same number of electrons
give the ion arrangement for sodium and state which element it is isotonic with
Na -1s^2 2s^2 2p^6 3s^1 Na+- 1s^2 2s^2 2p^6 isotonic with Neon
why is there a general increase in the first ionisation energy across a period?
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.
why would there be a large drop in ionisation energy between Helium and Lithium?
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.
why would there be a slight drop in ionisation energy between Beryllium and Boron
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
on the graph between from Boron to Nitrogen, why is there a slight increase in ionisation energy?
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
why would there be a slight dip in the ionisation energy between nitrogen and oxygen?
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.
what is the trend in ionisation energy going down a group and why?
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)
what is the formula for nitric acid and which are the ions involved?
HNO3: H+ NO3^-
what is the formula for carbonic and which are the ions involved?
H2CO3: H^2+ CO3^2-
what is the formula for Phosphoric acid and which are the ions involved?
H3PO4: H^3+ PO4^3-
what is the formula for sodium hydroxide and which ions are involved?
NaOH: Na+ OH-
what is the formula for Ammonium and which ions are involved?
NH4OH: NH4+ OH-
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
- 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
what is the formula for hydrochloric acid? and which are the ions involved?
HCl: H+ Cl-
what does it mean to have a noble gas electron arrangement
the chemical has a full outer shell of electrons
