P - Atomic Structure Flashcards
Electron configuration of Cr (Chromium)
1s²2s²2p⁶3s²3p⁶4s¹3d⁵ –> 6 unpaired e- –> more stable
Electron configuration of Cu
1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰
Aufbau Principle
e- enter the lowest energy orbital possible.
Hund’s Rule
e- only pair up when no empty orbitals of the same energy are available.
Symbols of mass number and atomic number
Mass number (A) and atomic number (Z)
First ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state.
Second ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous 1+ ions.
Electron impact ionisation
Vaporised atoms are passed into a vacuum chamber,
where high energy electrons are fired at them,
knocking 1 electron from each of them to form a 1+ ion.
Electrospray ionisation
High molecular mass compounds are dissolved in water or a volatile solvent,
injected through a positively charged needle at high voltage,
the spray emerging with the solvent losing an electron to form a positive ion.
Isotopic abundances
The relative proportions of the stable isotopes of each element.
Give an example (formula) for first ionisation energy.
Na(𝗴) –> Na+ (𝗴) + e-
ENDOTHERMIC
Considerations for IE**
- size of nuclear charge
- distance of e- from nucleus
- shielding (by inner e- & nucleus)
Why is second IE higher than first IE?
First IE- removing e- from 𝙣𝙚𝙪𝙩𝙧𝙖𝙡 atom
Second IE- removing from 1+ 𝙞𝙤𝙣
𝙞𝙢𝙗𝙖𝙡𝙖𝙣𝙘𝙚: 𝙥𝙧𝙤𝙩𝙤𝙣𝙨 > 𝙚-
(∵ removed e-)
Describe the trend for first IE across the PERIOD.
Increases, as:
1. ↑ protons in nucleus
∵ ↑ nuclear charge
2. Atoms get smaller-
∵ ↑ force of attraction betw. nucleus & outer e-
(2 up –> 1 down)
Eg. Period 3
1. Al < Mg
∵ outer e- in 3p- 1. ↑ energy 2. further from nucleus
∴ ↓ energy to remove
- S < P
∵ 3p⁴ has 2 PAIRED e- ∴ repulsion- ↓ attraction to nucleus- ↓ energy to remove 1 from the pair than unpaired -easier =)
> increased shielding- negligible
∴ each successive e- enters same shell
Describe the trend for first IE down the GROUP.
- ↑ shielding
- ↑ distance from nucleus
∴ weaker attraction from nucleus to outer e-
How to determine what group the element it’s in from its successive ionisation energies?
Look for big jumps (eg. big jump from 2nd to 3rd –> group 2)
No apparent jump- group 0
Why is it necessary to ionise atoms before acceleration?
Particles have to be charged before attraction to a charged plate/ electric field.
What deflects ions in a mass spectromter?
Magnetic field.
What is adjusted in order to direct ions with different m/z ratio onto the detector?
Magnetic field (/ strength of magnet)
What accelerates positive ions before they are deflected?
Electric field.
What factor, other than the mass to charge ratio of an ionised particle, determines how
much that particle is deflected in a magnetic field of a given strength?
Speed.
Relative isotopic mass
Mass of the ISOTOPE relative to 1/12th the mass of an atom of Carbon-12.
Isotopes of Cl
Cl-35 : Cl-37 = 3:1
m/z: 70 72 74
9 : 6 : 1
What is the purpose of a detector in a mass spectrometer?
To detect POSITIVE IONS.
Why do ions separate into different paths in a M. S.?
Diff. isotopes.
For each type of ion, what 2 measurements can be made from the mass spectrum?
- m/z
- Abundance
Formula of a ion
eg. C3H5O2N
C3H₆O2N+/ C3H5O2N𝑯+
Write an equation for the electrospray ionisation of element X.
X (g) + H+ (g) –> XH+ (g)
Write an equation for the electron impact ionisation of element X.
X(g) + e- –> X+(g) + 2e-
How are particles accelerated in a mass spectrometer?
attracted to a -ve charged plate
How many decimal places are included on low res mass spectrometry?
1
How does high-res mass spectrometry allow us to identify compounds?
- measured to 5 d.p.
- see small diff. that low res x pick up
When building a half equation, what is the first thing you balance?
species w/ variable oxidation state.
After combining half equations, what should you remove?
spectator ions
