Topic 1: Atomic Structure & The Periodic Table 1️⃣ Flashcards
What is the definition of relative atomic mass ?
The weighted mean mass of an atom of an element relative to the 1/12th the mass of a carbon-12 atom
What are isotopes
Atoms of the same element with the same number of protons but a different number of neutrons
What has to be done in order to calculate the relative atomic mass?
Chemical analysis (mass spectrometry) is carried out.
Gives us info on the relative abundance of each isotope in the sample
What does a mass spectrometer measure
The masses of atoms and molecules (as well as the fragments that make the molecule up)
On a mass spectrometry graph how do we calculate relative atomic mass when y axis is %
(Mass x abundance)+(mass x abundance)
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100
On a mass spectrometry graph how do we calculate relative atomic mass when y axis is relative abundance instead of percentage abundance?
(Mass x abundance) + (mass x abundance)
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Sum of isotopic abundances (peaks on graph)
what does the molecular ion peak (peak furthest to the right) tell us ?
Relative molecular mass
What are the 4 stages of mass spectrometry
Ionisation
Acceleration
Deflection
Detection
Why must the ionisation chamber in mass spectrometry be a vacuum?
If there were any loose gas particles they would be ionised and picked up on the detector which would interfere with results
What is important about the sample in mass spectrometry
The sample must be vaporised so that all particles are in a GASEOUS state
Describe how ionisation works in a mass spectrometer
Sample is inserted and bombarded with a beam of high energy electrons.
Electrons are knocked off- creates positive ions
Why must the sample be ionised (mass spectrometry)
Must be positive ions in order to get detected
How are the ions accelerated (mass spectrometry)
Electric field helps accelerate the ions
What helps deflection (mass spectrometry)
Magnetic field created by an electromagnet - bends the path of ions
What can you find out from position of detection? (Mass spectrometry)
The larger the mass of the ions, the less they are deflected and the position of detection depends on amount of deflection
What is the order of how shells are filled
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f
What do the coefficient, the letter and the power represent eg. 3s^2
3 - quantum shell
s- type of orbital
2- number of electrons
What is the maximum amount of electrons an s-orbital can hold
2
What is the maximum amount of electrons a p-orbital can hold?
6
What is the maximum amount of electrons a d-orbital can hold?
10
What is the maximum amount of electrons an f-orbital can hold?
14
What is the shape of an s-orbital
Spherical
What is the shape of a p-orbital
Figure of 8
Aligned along perpendicular axes
How many types of d orbital are there
5
Why does the 4s orbital fill before the 3d orbital
The energy level of 4s is slightly lower than 3d
What makes copper an exception to the rule of shell filling ?
3d orbital fills fully before the 4s orbital
What makes chromium an exception to the rule of shell filling ?
The orbitals 3d and 4s are only half-filled
What do we need to remember when emptying the orbitals ?
Although in most cases (bar 2 exceptions) 4s fills before 3d, when emptying the 4s empties before the 3d orbital
What is Hunds rule of electrons in boxes ?
States that electrons will occupy the orbitals singularly before pairing takes place
What is the Pauli Exclusion Principle ?
States that 2 electrons cannot occupy the same orbital unless they have opposite spins.
How is the direction of electron spin shown?
Upwards and downwards arrows
How can you tell which block an element is in from looking at their electronic configuration?
Example : If it ends in 3d then it is in d-block
If it ends in 4s it is in s-block
Define 1st Ionisation energy
The energy required to remove 1 electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
How is atomic radius a factor in removing electrons ?
The more shells an atom has, and therefore the further away the outer electrons are from the nucleus, the less attraction they experience (easier to remove electrons)
How is nuclear charge a factor in removing electrons ?
The more protons, the greater nuclear charge, the greater the attraction felt by the outer electrons (harder to remove)
How is electron shielding a factor in removing electrons ?
As the number of electrons between outer electrons and nucleus increases, the outer electrons feel less attraction towards the nuclear charge (easier to remove)
What is the general trend in ionisation energies down a group
Generally decrease
What is the general trend in ionisation energies across a period
Ionisation energy generally increases due to increased nuclear charge and the fact that the electrons being removed are from the same sub-shell and therefore have similar shielding.
Drops slightly between groups 2&3 and 5&6
Explain the drop in ionisation energy between groups 2 & 3
In a group 3 element, the highest energy (outer) electron occupying a 3p rather than a 3s orbital.
3p has a slightly higher energy so it is slightly further away from the nucleus. It also experiences additional shielding from the 3s orbital.
Both factors override the effect of an extra proton (increased nuclear charge) and result in a drop of ionisation energy
Explain the drop in ionisation energy between groups 5 & 6
The electrons being removed from both group 5 & 6 elements are from p-orbitals.
However, the electron being removed from the group 6 element comes from a paired orbital whereas the electron being removed from a group 5 element comes from a singly paired orbital.
The extra repulsion between paired electrons in the group 6 element makes it easier to remove the one electron ( less energy is needed)
What is the successive ionisation energy
Measure if the energy required to remove each electron in turn
Why is each successive ionisation energy greater than the last?
As each electron is removed the ion becomes increasing positive
As each electron is removed there is less repulsion between the electrons and each shell will be drawn slightly closer to the nucleus
As the distance of each electron from the nucleus decreases slightly the nuclear attraction increases.
What do large jumps on a successive ionisation energy graph represent
A change in shell
What do dots on a successive energy graph represent
Electrons
How can you work out the group number from looking at a graph showing successive ionisation energies
The number of electrons before the first big jump
What does the group number tell us
The number of electrons in the outer shell
What does the period tell us about the element
The total number of shells
Where are s-block elements located on the periodic table
Groups 1 & 2 and helium
Where are the p block elements located on the periodic table
Right hand side bar helium
Where are the d-block elements located on the periodic table
Transition metal area (centre)
As you go across the metals (Li, Be, Na, Mg, Al) explain how the melting and boiling points are affected
Melting and boiling points increase as metallic bonds get stronger due to…
More delocalised electrons per metal cation and atomic radius decreases
Explain why the melting and boiling points peak (C, Si)
Macromolecules (giant covalent ) have very strong covalent bonds
Explain why melting and boiling points decrease (N,O,F,P,S,Cl)
These elements are simple molecular structures and have weak London forces which are easily overcome
Explain why the noble gases have the lowest melting and boiling points
They are monoatomic elements - have very weak London forces between the atoms
Explain the term orbital
Sub shells were an electron is likely to be found
What is periodicity
The trends in properties of elements as you go across the periods of the periodic table
What happens to I.E at the start of a new period
Falls dramatically
Define relative isotopic mass
The mass of an atom of an isotope relative to 1/12th the mass of a carbon-12 atom
