Atomic Structure and the Periodic Table Flashcards
What is an isotope?
An isotope can be defined as an atom of an element with a different number of neutrons.
What remains the same about all isotopes of the same element?
They all have the same number of protons (making it the same element) and the same number of electrons.
What properties of isotopes remain the same and why?
Their chemical properties remain the same due to them all having the same number of electrons.
What properties of isotopes change and why?
Their physical properties change due to them having different number of neutrons. For example, carbon-14 is radioactive but no other carbon isotopes are.
Relative atomic mass is what?
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.
Weighted mean mass takes into account what?
The percentage abundance of each isotope and the relative isotopic mass of each isotope.
Relative isotopic mass means what?
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.
Cl-35 has abundance of 75.78%.
Cl-37 has abundance of 24.22%.
What is the RAM of Cl.
(75.78x35)/100 + (24.22x37)/100
35.4844 = 35.5 (1dp)
To calculate the relative molecular mass we do what?
Add together the relative atomic masses of each of the atoms in the molecule.
To calculate the relative formula mass we do what?
Exactly the same as relative molecular mass (add together the relative atomic masses of each of the atoms), just on larger molecules.
What instrument can we use to measure percentage abundances?
A mss spectrometer.
A mass spectrometer measures what?
The masses of atoms and molecules (as well as fragments that make the molecule).
Mass spectra is what?
The graph/results at the end of using the mass spectrometer.
What is the molecular ion peak (M+)?
The strongest peak to the right on a mass spectra.
The M+1 is what?
A result of other isotopes in the sample and appears to the right of the M+.
What is the order for mass spectrometry?
Vapourisation Ionisation Acceleration Deflection Detection
Why are samples vapourised for mass spec?
The sample needs to be gaseous for mass spec to work.
Why are particles ionised for mass spec?
The particles need to be positively charged for them to be accelerated. They are subjected to a beam of high energy electrons.
What happens in the ioniser in mass spec?
The ioniser is a vacuum and the sample is subjected to high energy electrons to ionise the sample. The electrons remove electrons from the sample to form positive ions.
What happens in the mass analyser in mass spec?
Ions are accelerated in a negative electric field then a magnetic field deflects the ions.
What does the detector do in mass spec?
Detects deflected ions, contains an electron multiplier and an amplifier to detect the deflection on ions by the magnetic field.
What do different rates of deflection in mass spec show?
Different rates of deflection by the magnetic field shows different atomic masses as more massive isotopes are deflected less by the magnetic field, whereas less massive isotopes are deflected more.
Electrons exist in what kind of shells?
Quantum shells.
The first quantum shell is where relative to the nucleus?
Closest to the nucleus.
Electrons that exist in the first quantum level have the lowest what?
Energy level.
Quantum shells can be divided into what?
Subshells.
The subshells contain orbitals. How many electrons can be held in each orbital?
2e- in each orbital.
How many electrons can be held in the 1st quantum shell and what is/are the orbital(s).
2e- held in the 1s subshell.
How many electrons can be held in the 2nd quantum shell and what is/are the orbital(s).
8e- held in the 2s and 2p orbitals.
How many electrons can be held in the 3rd quantum shell and what is/are the orbital(s).
18e- in the 3s, 3p and 3d orbitals.
How many electrons can be held in the 4th quantum shell and what is/are the orbital(s).
32e- held in the 4s, 4p, 4d and 4f orbitals.
S-orbitals are what shape?
Spherical.
P-orbitals are what shape?
Dumbell shapes along each axis.
D-orbitals are what shape?
There are five different d-orbital shapes.
What shapes are f-orbitals?
There are 7 different f-orbital shapes.
Why does the 4s orbital fill before the 3d orbitals?
Because the energy level of 4s is lower than that of 3d.
What are the exceptions to the rule of the 4s filling before the 3d?
The exceptions are chromium with 24e- and copper with 29e-.
What should we remember about emptying the 3d and 4s orbitals?
Despite 4s filling before 3d, when ions are formed the 4s empties before the 3d.
What is Hund’s Rule?
Electrons will occupy the orbitals singly before pairing takes place.
Pauli Exclusion Principle is what?
Two electrons cannot occupy the same orbital unless they have opposite spins.
What are the common metal positive ions and their emission spectra?
Copper-blue/green Barium-apple green Calcium-brick red Potassium-lilac Sodium-yellow Strontium-red Lithium-crimson
What is the final colour of an atomic emission spectra a result of?
The final colour of an atomic emission spectra is the result of individual colours produced.
What instrument can be used to measure atomic emission spectra?
A spectroscope.
What part of atomic emission spectra can we see?
We can only see the visible part of the atomic emission spectra as these are wavelengths emitted in the visible part of the EM spectrum. Other wavelengths are emitted outside the spectrum by other positive ions.
What causes atomic emission spectra?
If an electron takes in energy from its surroundings it can be excited to a higher energy level. When they drop down to a lower energy level they release energy as a photon.
Energy levels have what kind of values?
Discrete values.
True or false, electrons can only be excited to one energy level.
False, electrons can be excited to any energy level and take a route of stopping at any energy levels on return to ground level.
There are no inbetween amounts of energy in atomic emission spectra suggesting what?
It suggests that electrons exist at very specific energy levels and that provides evidence for quantum shells existing.
First Ionisation energy can be described as what?
The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of 1+ ions.
For ionisation equations the mole of atoms/ions must be in what state?
Gaseous state.
For ionisation energy equations you must refer to how much of the substance?
A mole.
The lower the first ionisation energy the what?
Easier it is to form an ion.
What effect does atomic radius have on I.E.?
The more shells an atom has, therefore the further away from the nucleus, the less attraction the electrons experience.
What effect does nuclear charge have on I.E.?
The more protons, the greater the nuclear charge, the greater the attraction felt by the outer electrons.
What effect does electron shielding have on I.E.?
As the number of electrons between the outer electrons increases, the outer electron experiences less attraction towards the nuclear charge.
Ionisation energies generally do what down a group?
Decrease.
Across a period ionisation energies generally do what?
Increase.
Why is there a drop in ionisation energies from groups 2 to 3?
The group 3 atom has its outer electron in the p-orbital rather than the s so it experiences additional shielding as well as being slightly further from the nucleus. These factors override the effect of the additional charge in the nucleus.
Whys is there a drop in ionisation energies from groups 5 to 6?
Shielding is similar in both groups and for both electrons are being removed from p-orbitals. However for the group 5 atom the electron is being removed from a singly occupied orbital whereas in group 6 this is being removed from a pair orbital with the repulsion between the electrons making it easier to remove one.
The anomalies in 1st I.E. are evidence for what?
Electron subshells.
Successive ionisation energy is a measure of what?
It is a measure of the energy required to remove each electron in turn.
The second ionisation energy of an atom can be defined as what?
The energy required to remove 1 electron from every ion in a mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
Why is each successive I.E. greater than the last?
As each electron is removed there is less repulsion between the electrons and each shell is drawn slightly closer to the nucleus.
As the distance of each electron from the nucleus decreases slightly, nuclear attraction increases, therefore more energy is required to remove each successive electron.
