Karteikarten
2. Atomic Structure
Karten in diesem Stapel (48)
- 1Relative charge of proton, neutron and electronProton: +1
Neutron: 0
Electron: -1 - 2Relative mass of proton, neutron and electronProton: 1
Neutron: 1
Electron: 1/2000 - 3Where are protons, neutrons and electrons located?Proton: nucleus
Neutron: nucleus
Electron: energy levels - 4What does an atom consist of?An atom consists of a nucleus, with protons and neutrons, that is surrounded by electrons.
- 5What does A stand for?Mass number
- 6What does Z stand for?Atomic number
- 7What is the atomic number?The number of protons in the atom's nucleus
- 8What is the mass number?The total number of protons and neutrons in an atom's nucleus
- 9What are protons and neutrons held together by?The strong nuclear force. Much stronger than electrostatic force.
- 10What are electrons held by?Electrostatic force of attraction that holds electrons and protons together.
- 11Define an isotope.Isotopes are atoms with the same number of protons but different number of neutrons. Different isotopes of the same element react chemically in exactly the same way as they have the same electron configuration. Isotopes vary in mass number because different no. of neutrons.
- 12Formula for number of electrons in each shell.2n^2
- 13Define an ion.Ions are electrically charged particles formed when atoms lose or gain electrons.
- 14Relative atomic massRelative atomic mass or Ar is the weighted average mass of an an element taking into account it's naturally occurring isotopes relative to 1/12 of the mass of carbon-12.
- 15Relative molecular massRelative molecular mass or Mr of a molecule is the mass of that molecule compared to 1/12 the mass of an atom of carbon-12.
- 16How to make ions for the mass spectrometer?1. *Electron gun* : fires high speed e- at sample which knock off electon(s) from sample
M(g) -> M+(g) + e-
2. *Electric field* : the sample is dissolved in a volatile, polar solvent. Sample is passed through a highly positively electrically charged hollow needle : this adds a proton from the solvent
M(g) + H+ -> MH+(g) - 17When would you use an electron gun to ionise?Used for elements
and substances with low formula mass.
Electron impact can cause larger organic
molecules to fragment. - 18When would you use electro spray to ionise?Used preferably for larger organic
molecules. The 'softer' conditions
of this technique mean
fragmentation does not occur. - 19What is mass spectrometry used for?Time-of-flight mass spectrometry is a method of mass spectrometry in which an ion's mass-to-charge ratio is determined via a time measurement.
- 20Explain each step in the time-of-flight mass spectrometer*Vacuum*
1. Whole apparatus is kept under a vacuum to prevent ions colliding with molecules from air.
*Ionisation*
*Acceleration*
2. Ions are accelerated by an electric field of known strength, positive ions -> negatively charged plate. Results in an ion having same Ke as any other ion with same charge.
*Ion Drift*
3.Velocity of an ion depends on mass-to-charge ratio
*Detection*
4. The time that is subsequently takes for the particle to reach a detector at a known distance is measured.
5. This time will depend on the mass-to-charge ratio of the particle (heavier particles reach lower speeds).
*Data analysis*
6. From this time and the known experimental parameters one can find the mass-to-charge ratio of the ion. - 21Explain how, in a mass spectrometer ions are detected and how their abundance is measured.Detected by positive ions collide with detector causing a current to flow. The abundance measured depends on the number of ions hitting detector.
- 22Describe how mass spectrometry can be used to determine relative molecular mass.In the mass spectrum, the heaviest ion is likely to be the molecular ion.
- 23What is the order in which orbitals are filled in?
- 24Define ionisation energyIs the energy required to remove electrons from a gaseous atom. As it is removing electrons it is an endothermic process.
- 25Define first ionisation energy1st IE is the energy required to remove one mole of the most looselt held electrons from one mole of gaseous atom to produce 1 mole of gaseous ions each with a charge +1.
- 26Equation for first ionisation energy.X(g) -> X+(g) + e-
- 27Equation for second ionisation energy.X+(g) -> X 2+(g) + e-
- 28What are the factors affecting ionisation energy?1. Distance of the electron from the nucleus. An electron close to the nucleus will be much more strongly attracted.
2.The number of electrons between the outer electron and the nucleus. The outer electron only feels a net pull of approximately 1+ from the centre in the case of 2.8.1 due to shielding. - 29Explain the general trend across periods 2 and 3 in IE1. IE increase across a period due to increase nuclear charge which causes greater attraction between the nucleus and electrons.
2. Also drags outer electrons close increasing IE
3. Similar shielding - 30Why the drop in IE between groups 2 and 3?1. IE decreases due to increased distance -> less attraction -> lower IE.
2. In period 2 - 2p orbital is only shielded by 1s but also 2s.
3. In period 3 - 3p covered by 3s and 2s - 31Why the drop in IE between groups 5 and 6?Paired electron in p orbital repel.
- 32Trends in ionisation energy down a group1. IE decreased due to atomic radius increases -> less attraction.
2. Increased shielding compensated for the extra proton. - 33Why has Helium the largest first ionisation energy?1. Its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells.
2. He has a bigger first ionisation energy than H as it has one more proton - 34Why is there a drop from the end of a period to the start of the next?1. Next element will have its outer electron in a shell further from the nucleus and it more shielded. So the next element's outer electron is easier to remove.
- 35Patterns in the second ionisation energyIf the graph of second ionisation or each successive element is plotted then a similar pattern to the first ionisation energy is observed but all the elements will have shifted one to the left.
- 36Why is Li second ionisation energy greater than HeLi has a bigger second ionisation energy than He as it has more protons
- 37How can mass spectrometers be used in space?Identify the composition of other planets
- 38What is an atomic orbital?A region of space around an atomic nucleus where there is a high probability of finding an electron
- 39How many electrons can a single atomic orbital hold?Two
- 40How many electrons do s, p , d and f - orbitals hold?s-orbital: 2
p-orbital: 6
d-orbital: 10
f-orbital: 14 - 41In which direction must 2 electrons in the same orbital spin?Opposite
- 42What do successive IE of Na tell you about the structure of it?1. One electron furthest away from the positive nucleus (easy to remove)
2. Eight electrons nearer in to the nucleus (harder to remove)
3. Two electrons very close to the nucleus (very difficult to remove because they are nearest to the positive charge of the nucleus.
4. Graph of log(IE) / electron removed doesn't show the eight electrons subdivided into 2 further groups. However IE / electron removed just does. - 43How would you calculate R.A.M from a spectra?R.A.M = Sum of:(isotopic mass x relative abundance) / total relative abundance
- 44Mass spectra for Cl2 and Br2
- 45How to get molecular formula when using the electrospray method?There will be one peak that will equal the mass of the MH+ ion. It will therefore be necessary to subtract 1 to get the Mr of the molecule. So if a peak at 521.1 is for MH+, the relative molecular mass of the molecule is 520.1.
- 46What exception is there when filling shells in the d-block?Chromium and copper have an unusual
arrangement in having a half filled 4s subshell. - 47Is the p or the s orbital emptied first in the d-block?When d-block elements form ions they lose the 4s electrons first.
- 48State why the precise relative atomic mass quoted in Table 1 for the 12C isotope is exactly 12.00000By definition
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- A2 Chemistry (Year 1 Physical) Karteikarten am 2. Atomic Structure, erstellt von Nikodem Czarlinski am 08/03/2019.
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