Atomic Structure 3.1.1 Flashcards
List the order of poeple and names of models of the atom
John Dalton -Solid sphere
JJ Thompson -Plum pudding model
Ernest Rutherford -Nuclear model
Niels Bohr -Bohr model
Edwin schrodinger -Quantum model
Explain each atomic structure model
John Dalton Solid Sphere: Different spheres make up different elements
JJ Thompson Plum pudding model: Discovered negative electrons, ball of positive charge with electrons embedded in it, electrons can be emitted from the atom and electrons are identical
Ernest Rutherford Nuclear Model: Alpha particle scattering experiment, fired positively charged alpha particles at thin gold leaf, most passed straight through, a small fraction rebounded back, small positive nucleus surrounded by electrons, most of the atom is empty spaced, problem is the electrons would attract to the positive nucleus so the atom would collapse
Niels Bohr Bohr Model: Electrons in fixed orbitals, each shell has fixed energy, clouds of electrons would spiral into the nucleus so atom would collapse
Erwin Shrodinger Quantum Model: Not all the electrons in the shell have the same energy, electrons are found in subshells, can’t tell where an electron is or it’s direction, complicated equation needed
What did James Chadwick discover
Neutrons
What is the relative mass of an electron
1/1840
Define mass number and atomic number
Mass number is the total number of protons and neutrons
Atomic number is the number of protons
Define isotopes and expand on their chemical and physical properties
Isotopes have the same number of protons but a different number of neutrons
Same chemical properties as they have the same electron configuration
Different physical properties as the number of neutrons is different so the mass is different(e.g. density, rate of diffusion)
Define the mass spectrometer
An analytical technique that is used to determine information about elements and Compounds. It can determine the Ar of isotopes and Mr of molecules and their abundance
Why is the mass spectrometer apparatus kept under a high vacuum
To prevent the ions that are produced from colliding with molecules from the air
What are the 4 key areas of the mass spectrometer
Ionisation area
Acceleration area
Ion drift area
Detection area
What are the 2 methods for ionisation
Electron impact
Electrospray
Explain electron impact
What is the equation for it given that X is the sample
-Vaporised sample is injected at low pressure
-High energy electrosn from an electron gun are fired at a sample
-Usually, one electron of knocked of from each particle forming a positive ion
X + e‐ -> x+ + 2e‐
X(g) -> x+(g) + e‐
Why is electron impact used for elements and substances with a lower formula mass
It causes larger molecules to fragment
Explain electrospray
Give the equation given that X is the sample
-Sample is dissolved in a volatile polar solvent(water/ethanol/methanol)
-The solvent acts as a source of protons(H+) and is injected through a needle and the tip of the needle has a very high voltage
-Particles are ionised by gaining a proton
-Solvent evaporates, leaving a positive ion
X + H+ -> XH+
Explain the acceleration area in the mass spectrometer
-The positive ions are accelerated by an electric field
-The elective field gives the same kinetic energy to all ions (ke = ½mv²)
-As all particles have the same kinetic energy, the velocity of each particle depends on its mass(lighter particles have a higher velocity, heavier particles have a lower velocity)
Explain ion drift in the mass spectrometer
The positive ions travel into a tube with no electric field
The ions are distinguished by their different flight times
Mass spectrometer
What is the formula t=
What is the formula v= (kinetic energy reearanged)
Merge these 2 formulas into 1
What does this tell tou about t and √m
t=d/v
V= √2ke/m
t=d√m/2ke
t and √m are proportional
Explain detection in the mass spectrometer
The positive ions hit the detector and generate a small current
The current is produced by electrons transferring from the detector to the positive ion
The size of the current is proportional to the abundance of the species
In the spectra for electron impact for elements, what do the peaks represent
The isotopes of the element
Why is there a 24Mg ²+ peak and what is the m/z on the spectra
It lost 2 electrons
12
Why is a series of peaks created if a molecule is put through a mass spectrometer with an electron impact ionisation
The molecule fragments
In the spectra for electron impact for molecules, what is special about the peak with the largest m/z
It is the molecular ion
It is the complete molecule and will be equal to the Mr
In Electrospray, if the m/z says 521.1, what is the Mr and why
520.1
A proton would bave been added so the m/z would be 1 greater than the Mr
What is the ratio and m/z for the mass spectra for Cl2 and Br2
What are the two isotopes for each and their proportion
9:6:1
70 72 74
1:2:1
158 160 162
35 Cl(75%) and 37 Cl(25%)
79 Br(50%) and 81 Br(50%)
Mass spectra SAMSUNG NOTES
Yayayyayay
What are the 4 equations needed in TOF calculations
t = d/v
v = √2ke/m
Moles = mass/Mr
No. Particles = moles × avagadros constant
What is avagadros constant (L)
6.022 × 10²³
Level one electrons are closest to the nucleus, describe their energy
Lowest energy
Orbitals can hold up to 2 electrons as long as they have…
Opposite spin(do not repel)
What is the order of subshells from lowest energy to highest energy
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
Why is the 4s subshell filled first, rather than the 3d subshell
4s subshell has less energy than 3d subshell
Which is special about the elements in the same groups as Chromium and copper (both transition metals) in electron configuration
They donate one of their 4s electrons to the 3d subshell to get a more stable 3d subshell
When transition metals become ions, which electron do they lose and why
They lose their 4s electrons before 3d as 4s has less energy than 3d
Define first ionisation energy
Define second ionisation energy
Why does higher ionisation energy means it is more difficult to forma positive ion
First ionisation energy: Energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms tk form 1 mole of gaseous 1+ ions
Second ionisation energy: Energy needed to remove 1 mole of electrons from one mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
A higher ionisation energy means it is more difficult to form positive ions as there is a high attraction between the nucleus and electron
What 3 factors affect ionisation energy and explain them
Nuclear charge: More protons means a stronger attraction between the outer electron and nucleus so electron is difficult to remove
Distance from nucleus: Electrons closer to nucleus, more stronger attraction between electron and nucleus
Shielding: More electrons between the nucleus and the outer electron, reduces the attraction between outer electron and nucleus
What is the trend of first ionisation energy as you go down Group 2 and explain it
The first ionisation energy decreases
Electron that is being removed is further from the nucleus and there is more sheilding
What is the trend of first ionisation energy as you go across period 3 and explain it
First ionisation energy increases
Nuclear charge(number of protons) increases + same shielding as electrons are being removed from the same shell
What two measurements does the mass spectrometer give
m/z value
Abundance
Explain the anomalies that are evidence for the existence of the s and p sublevels
Magnesium -> Aluminium
Phosphorus-> sulfur
MAGNESIUM -> ALUMINIUM
-The outer electron in aluminium is in a 3p orbital which has a slightly higher energy than the 3s orbital
-The 3p orbital has additional sheilding provided by the 3s orbital
-Therefore, less energy is removed from the electron
PHOSPHORUS-> SULPHUR
-In sulphur, the 3p orbital contains a pair of electrons
-They repel eachother, making the electron easier to remove
SUCCESSIVE IONISATION ENERGY
Why is second ionisation energy always bigger than first ionisation energy
When the first electronic is removed, a positive ion is formed. The positive ion increases the attraction on the remaining electrons so the energy needed to remove the next electrons is larger
What does it mean when there is a large jump in ionisation energy
Electron is being removed from a new shell that is closer to the nucleus
