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Metals have a number of physical properties which make them useful to us in society, and which you will be familiar with from everyday experience. By considering the structure and bonding of metals which you have studied, we can explain these properties.
Metals are strong, with high melting and boiling points
Metals have high melting and boiling points as a result of the strong electrostatic attraction between the positively charged metal ions (we call positively charged ions cations), and sea of delocalised electrons. A great deal of heat energy is required to overcome this strong electrostatic attraction, which gives metals their high melting and boiling points.
Metals conduct electricity
The delocalised electrons in the metal are free to move throughout the entire structure. When attached to an electrical power source, this means the metal can conduct electricity.
Metals are workable
Metals have a crystal lattice, where the cations are arranged in a regular array. This means that when a large force is applied to a metal, the particles slide over each other (keeping their regular arrangement), and stay in their new positions.
Metals are normally easy to shape since this regular packing allows ions to slide over each other. Metals are therefore said to be malleable (easily beaten into shape), and ductile (easily pulled out into wires).see more
A mass spectrometer is an important analytical instrument which scientists can use to identify the amount and type of different chemicals in a substance. In this explanation I’ll go through how the mass spectrometer works.
There are four stages in a mass spectrometer which we need to consider, these are – ionisation, acceleration, deflection, and detection. Let’s go through these in order.
The sample needs to be vapourised first, before being passed into the ionisation chamber. Here, an electrically heated metal coil gives off a stream of electrons. The atoms or molecules in the sample are bombarded by this stream of electrons, and in some cases, the collision will knock an electron from the particle, resulting in a positively charged ion. Most of the ions formed have a +1 charge, as it is difficult to remove a second electron from an already positive ion.
The positively charged ions are repelled from the ionisation chamber (which is positively charged), and pass through negatively charged slits which focus and accelerate this into a beam.
The stream of positively charged ions are then deflected by a magnetic field. The amount ions are deflected by depends on
-the mass of the ion (lighter ions will be deflected more than heavier ones)
-the charge of the ion (ions with a greater charge than +1 are deflected more)
We can consider these properties as a mass/charge ratio (m/z), where the mass of the ion is divided by its positive charge.
By varying the strength of the magnetic field, the different ion streams (after deflection) can be focused on the ion detector, in order of increasing mass/charge ratio (as the lightest ions would need to be deflected the less). When an ion hits the detector, the charge is neutralised, and this generates an electrical current. This current is proportional to the abundance of the ion, these are sent to a computer for analysis.
A mass spectrum is generated, which shows the different m/z values of ions present, and their relative abundance.
Now you know has a mass spectrometer works – just remember the four stages in order – ionisation, acceleration, deflection, and detection. You should make sure to study a diagram of a mass spectrometer – a frequent question can be asking you to sketch a diagram, or describe how a particular step works, before then going on to interpret a mass spectrum.see more