Unit 3.1.1 - Atomic Structure Flashcards
What does atomic number mean?
It is the number of protons in the nucleus of an atom
What does mass number mean?
It is the sum of the number of protons in the nucleus of an atom?
What is the mass of an electron?
1/1840
What is an isotope?
Atoms with the same atomic number but different mass number
What is an ion?
Species in which the proton and electron numbers are not the same and so have an overall charge
What was Dalton’s model for the atom?
Solid spheres surrounded by an atmosphere of heat, different spheres made up different elements
What was Thomson’s model for the atom?
“The Plum Pudding Model” - Negatively charged electrons surrounded by a sphere of positive charge
What are Rutherford’s model for the atom?
There was a positively charged nucleus surrounded by orbiting electrons
How was Bohr’s different to Rutherford’s model?
The electrons didn’t just orbit the nucleus they occupied shells
What did Rutherford find from his experiment - firing alpha particles at a thin sheet of gold?
According to the plum pudding model they expected all the alpha particles to be slightly deflected by the positively charged sphere, however most passed straight through and only a small number were deflected. This meant most of an atom was empty space and there was only a small positive nucleus, this helped him to come up with his model for the atom
Define the relative atomic mass of an atom?
The average mass of one atom compared to 1/12th of the mass of one atom of carbon-12
Define the relative isotopic mass of an isotope?
The average mass of one atom of that isotope compared to 1/12th of the mass of one atom of carbon-12
What can you use to measure the relative abundance of isotopes and what graph does it produce?
Mass spectrometry and a mass spectra
Label the different sections in a mass spectrometry?
See flash card 12
What are the five sections in a mass spectrometry?
Vaporisation, ionisation, acceleration, deflection and detection
What happens during vaporisation in a mass spectrometry?
The sample is heated so that it is vaporised into a gas
What happens during ionisation in a mass spectrometry?
High energy electrons are fired out of an electron gun towards the sample to knock of electrons and turn them into ions
What happens during acceleration in a mass spectrometry?
The positive ions are accelerated by an electric field
What happens during deflection in a mass spectrometry?
The ions are deflected around the bend by a magnetic field
Which ions are deflected more during deflection?
Light ions with a smaller m/z ratio
What happens during detection in a mass spectrometry?
When ions hit the detector they cause a current to flow, the bigger the current produced the more of that isotope present in the sample
How can you get different ions to reach the detector during a mass spectrometry?
Alter the strength of the magnetic field so that different ions are deflected to the detector
What happens if you put molecules into a mass spectrometer?
The molecules often break up into fragments because of the high temperatures and conditions
What two things does a mass spectra show?
- ) the m/z ratio of the isotopes
2. ) the relative abundance of the isotopes
Do isotopes have similar or different chemical properties and why?
Similar because they have the same electron configuration
The shells that electron occupy are also known as?
Energy levels
Shells can be broken up into?
Sub - shells
Name the sub shells and orbitals in the first 4 shells?
1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f
How many electrons can an s, p and d orbitals hold?
2, 6, 10
Why do you fill from the 4s orbital before the 3d orbital?
Because the 4s has a lower energy level and you always fill the lowest energy level first
What two methods can you use to show electron configuration?
Orbital method and the box and arrow diagrams
What does the orbital method look like and what does it show?
It shows the energy level, then the sub shell and the number of electrons in the orbital in subscript
1s2, 2s2, 2p6, 3s2, 3p6, 4s2
What are the three rules for when drawing box and arrow diagrams?
- ) electrons fill the lowest energy sub shells first
- ) electrons fill the orbitals singularly before they start sharing
- ) when two electrons occupy the same orbital they must do with opposite spin and so the arrows must go in opposite directions
Which two elements don’t follow the usual electron configuration rules?
copper and chromium
Why doesn’t copper follow the usual electron configuration rules?
As it is more happier with a more stable full d sub shell
Why doesn’t chromium follow the usual electron configuration rules?
As it is more happier with a more stable half full d sub shell
What rule don’t chromium and copper follow?
Filling the 4s orbital before the 3d orbital
What is the electron configuration of copper?
1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1
What is the electron configuration of chromium?
1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1
Define first ionisation energy?
The energy needed to remove 1 electron from one mole of gaseous atoms to produce one mole of gaseous ions
What is the general formula or first ionisation energy?
Y (g) ————> Y+(g) + e-
Is ionisation energy exothermic or endothermic?
Endothermic
What is ionisation energy endothermic?
Because energy is required to overcome the attraction between the electrons and the nucleus and so energy is taken in
What four factors affect first ionisation energy?
Nuclear charge, shielding, distance from the nucleus and electron repulsion
How does nuclear charge affect first ionisation energy?
The more protons in the nucleus the greater the positive charge and so greater the attraction to the electrons and so they are harder to remove
How does distance from the nucleus affect first ionisation energy?
Electrons further away from the nucleus are less attracted to the nucleus and so are easier to remove
How does shielding affect the first ionisation energy?
As the number of electrons between the outer electrons and the nucleus increases the outer electrons feel less attraction and so are easier to remove
How does electron repulsion affect the first ionisation energy?
Electrons repel each other when they are in the same orbital and so electrons are easier to remove is they occupy an orbital with another electron
Why is second ionisation energy usually always more than first ionisation energy?
It is harder to remove an electron from a positively charged ions because the forces of attraction to the electrons will be greater
What is the general pattern in first ionisation energy as you go down group 2?
It decreases
Why does first ionisation energy decrease as you go down group 2?
There are more electron shells and so an increasing atomic radius and shielding meaning the outer electrons are less strongly attracted to the nucleus and are easier to remove
