Atomic Structure Flashcards
What are isotopes?
Isotopes are atoms with the same number of protons but a different number of neutrons, hence a different mass number.
What are principle energy levels?
Where the shell or orbital which the electron is located relative to the atom’s nucleus.
What does it mean for an element to be in a s/p/d/f block?
The outer electron is filling a s/p/d/f sub-shell.
Definition of first ionisation energy?
The first ionisation energy is the enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge.
What to remember when writing first ionisation energy equations?
State symbols
charges and electrons
H(g)= e⁻ + H⁺(g)
What are the three factors which affect first ionisation energy?
The attraction of the nucleus. (The more protons the greater the attraction)
The distance of the electrons from the nucleus. (The bigger the atom, the further the outer electrons are from the nucleus and the weaker the attraction of the nucleus)
Shielding of the attraction of the nucleus (Electrons being repelled by electrons in complete inner shells)
Why are successive ionisation energies always larger?
When the first electron is removed a positive ion is formed, the ion increases the attraction on the remaining electrons and so the energy required to remove the next electron is larger.
In a first ionisation energy versus electrons removed graph, why does a big jump between the 3-4 electron say its group is group 3?
Once the 3rd electron is removed the next electron to be removed is closer to the nucleus and so requires more energy to remove.
Why has helium got the largest first ionisation energy?
It has two electrons in its first/outer shell and requires lots of energy to remove as it is right next to the nucleus.
Why do first ionisation energies decrease down a group?
The number of shells increases and so there is less attraction to the nucleus and so requires less energy to remove an electron.
Why is there a general increase in first ionisation energy across a period?
Electrons are being added to the same shell the same distance from the nucleus however this increases the number of protons and so the attraction of the nucleus increases.
Why do group 1 elements have a significantly lower first ionisation energy than noble gases?
They have an electron further from the nucleus which has more shielding and so requires less energy to remove compared to the noble gas having a full outer shell with a greater attraction to the nucleus.
On a first ionisation energy x electrons removed graph why is there a small drop from Mg to Al?
Al is staring to fill a 3p sub-shell, whereas Mg has its outer electrons in the 3s sub-shell. The electrons in the 3p sub-shell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons.
When should you use electrospray ionisation for ionisation over electron impact?
When it is a larger organic molecule as it would fragment if you used electron impact.
How does electron gun ionisation work?
Electrons are fired at atoms (gaseous) knocking off an electron forming a positive charge, they are then accelerated in an acceleration area to the same kinetic energy before they are released and pass through the ion drift area and are then detected by an ion detector.
How does electrospray ionisation work?
The sample is dissolved in a volatile, polar solvent and then passed through a fine hypodermic needle which is positively charged and gives a proton to the sample.
How can you tell about the abundance and mass of the isotopes in the sample?
There will be greater currents when the abundance is higher and there will be spikes at different times depending on the mass ( higher mass isotopes are detected later as they are slower)
Why are there 3 peaks of chlorine isotopes if there are only 2 main isotopes?
Chlorine has two isotopes of Cl35 (75%) and Cl37 (25%) and can combine in 3 different ways.
When measuring the Mr of a molecule which peak should you choose to work out the formula of the molecule?
Choose the one furthest to the right of the graph and use that to work out the formula.
If electrospray ionisation was used for the electrospray ionisation of a molecule why is the final Mr value incorrect?
If electrospray ionisation was used for the ionisation of a molecule remember to minus one as a proton is added at the beginning.
Why is there a small drop from P-S?
With P there are 3 electrons filling the p sub-shell and when another one is filled there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.
Why do substances need to be ionised?
To accelerate the atoms
To bend the beam
Explain why the second ionisation energy of boron is higher than the first ionisation energy?
The electron is being removed from a positive ion which requires more energy to remove.
Explain why the second ionisation energy of boron is higher than the first ionisation energy?
The electron is being removed from a positive ion which requires more energy to remove.
What element in period 3 has the highest second ionisation energy and why?
Sodium
The second electron is being taken from a full outer shell which requires the most energy to remove.
What to remember when writing first ionisation energy equation?
The reactant is gaseous and so is the ion.
Equation for hypodermic needle?
A(g) + H⁺(g) → AH⁺(g)
