Mass Spectrometry

Used to measure the atomic or molecular mass of different particles in a sample.

This is like totally awesome because chemists can demonstrate how badass they are by doing CSI stuff with it.

Now there are many different mechanisms in which Mass Spectrometry can be done through, but because you’re just a dim-witted student, you only need to know one. Funnily enough referred to as “Mass Spectrometers”.

Those things sound like they come from Star Wars, but really if you break them down, they’re just as complex as a toaster. Not that you, as a dim-witted student would know how a toaster works. Did you know that the adjusters on toaster are actually timers in minutes, not power levels which is the common misconception.

Breaking a Mass spectrometer down, you’d find three main parts,

An Ioniser, or if you’re feeling Fat and Patriotic, you could call it an Ionizer. All the same: The ioniser is where the sample goes after being injected from a sample inlet for it to get turned into ions, clue is in the name. This is done by bombarding the little stream of sample with electrons. ELECTRONS EVERYWHERE. Btw, if you put the word “Sea of electrons” you deserve to die, because that’s not acceptable A level Chemistry terminology, but since you’re a dim-witted student, the examiner might let you off.

General formulae for what happens in the ioniser zone of a mass spectrometer:

X_(g) + e^- à X⁺_(g)+ 2e^-

The Analyser, or if you’re a fat patriot, you might know it as the analyzer, is the second component in a Mass Spectrometer.

The crap thing about the analyser for a student is that there are so many different types of it. The one you should bear in mine is the one that measures time of flight of the ions. Basically, ions are accelerated using whatever method, usually a magnetic pulse, so that they’re all strolling with the same level of energy, in the same direction, and the fatter ions take longer than the skinny ions to cross a certain distance. This is called measuring the “Time of flight”.

After the ions go through the analyser, and get all analysed and so forth, they go into the Detector chamber, where ions are deteced by an ion detector. The detector produces a varying electric current depending on the ion it got hit with, and the “computer” registers this as a piece of data which eventually gets compiled into an Abundance/Charge graph, aka Mass Spectra!

Molecular shape structures - As far as an A level student needs to know.

Tetrahedral

(E.g. Methane CH4)

109 degrees apart.

Pyramidal

(E.g. Ammonia)

109 degrees apart.

Bent

(E.g. Water)

104 degrees apart.

Linear

(e.g. BeCl2)

180 degrees apart

Planar Triangular 

(E.g. BF3)

120 degrees apart, and two dimensional

Trigonal bipyramidal

(E.g. Phosphorus Pentachloride)

120, or 90 degrees apart

Octahedral

(E.g. Sulfur hexafluoride)

90 degrees apart on all planes.

Quick Guide to Molecule Shapes

A general example in Methane:

Where the firm lines resemble what lies on the 2D plane.

The dotted line resembles what lies backwards.

The Wedge resembles what lies forwards.

Making Methane actually look like this:

We use these denotations because molecules in real life are actually 3 Dimensional. 

n.b. Lone pairs are very important in atoms in molecules because they define what else the atom can bond with.

Blending fuels

This is the process that takes place in an engine (By the piston):

1-      Input               (Remember as “Suck”)

2-      Compression (Remember as “Puff”)

3-      Explosion        (Remember as “Bang”)

4-      Exhaust           (Remember as “Blow”)

Knocking in engines occurs when a fuel with a low octane number is used.

Knocking is the pre-ignition of fuel.

Fuel’s ignitability must be in sync with the piston performance, otherwise knocking will occur, damaging the engine.

Octane numbers

Measurements of pre-ignition. (How likely is it for a fuel to pre ignite)

The scale goes from 0 to 100, with some fuels being in the negatives, or even +100.

Example of a 100 is 2,2,4- trimethylpentane.

Example of a 0 is Heptane.

Fraction columns generally produce fuels of 40-60 octane numbers. While modern engines require 95-98. Therefore fuel must be manufactured in order to give it a greater Octane value.

Octane numbers increase as the Hydrocarbon chain becomes shorter, and/or more branched.

We can shorten hydrocarbon chains via Cracking.

E.g. C₂₀ H₄₂ à C₈H₁₈ + C₁₂H₂₄

We can increase branching via Isomerism.

We can also use reforming  to create cycloalkanes from hydrocarbon chains.

Electronic Structure In Shells

L.O. Define what a shell is.

L.O. Understand how they’re filled.

L.O. Explain and Describe the different types of bonding.

Neil’s idea of Levels became outdated and out-fashioned because it was too simple. This is when the idea of Shells came in.

Shells are groups of orbitals.

This is a more complex concept because the levels idea only includes distance measurements – but no shape or location values …etc

N=1 is the first shell. Contains 2 electrons.

N=2 is the second shell. Contains 8 electrons.

N=3 is the third shell. Contains 18 electrons.

Etc

You can only get S orbitals in n=1.

You can only get S and/or P orbitals in n=2.

You can only get S and/or P and/or D orbitals in n=3.

Etc

	Atomic Number	N=1	N=2	N=3	N=4
Hydrogen	1	1
Helium	2	2
Lithium	3	2	1
Beryllium	4	2	2
Boron	5	2	3
Carbon	6	2	4
Nitrogen	7	2	5
Oxygen	8	2	6
Fluorine	9	2	7
Neon	10	2	8
Sodium	11	2	8	1
Magnesium	12	2	8	2
Aluminium	13	2	8	3
Silicon	14	2	8	4
Phosphorus	15	2	8	5
Sulfur	16	2	8	6
Chlorine	17	2	8	7
Argon	18	2	8	8
Potassium	19	2	8	8	1
Calcium	20	2	8	8	2
Scandium	21	2	8	9	2
Titanium	22	2	8	10	2
Vanadium	23	2	8	11	2
Chromium	24	2	8	12	1
Manganese	25	2	8	13	2
Iron	26	2	8	14	2
Cobalt	27	2	8	15	2
Nickel	28	2	8	16	2
Copper	29	2	8	18	1
Zinc	30	2	8	18	2
Gallium	31	2	8	18	3
Germanium	32	2	8	18	4
Arsenic	33	2	8	18	5
Selenium	34	2	8	18	6
Bromine	35	2	8	18	7
Krypton	36	2	8	18	8

n.b. The Group Number of an element is equal to the amount of electrons in its outermost shell.

Ionic Bonding	Covalent Bonding	Metallic Bonding
A metal, and a nonmetal	2 non metals	2 metals
Gain or loss of electrons	Sharing electrons	Sharing electrons

The objective of any bonding process is for atoms to become stable via filling their outermost shells.

Polarity & Electronegativity

The electron pairs shared between two atoms are not necessarily shared equally.

Bond polarity is a useful concept for describing the sharing of electrons between atoms.

A non-polar covalent bond is one in which the electrons are shared equally between two atoms.

A polar covalent bond is one in which one atom has a greater attraction for the electrons than the other atom. If this relative attraction is great enough, then the bond is an ionic bond.

Electronegativity of an atom is its ability to attract electrons to itself.

Dative bonding is when one element in a compound donates both electrons required for the bond to take place.

An example of this is Nitrous Oxide.