Topic 1 - Atomic Number, Mass number and Mass Spectrometry. Flashcards
What is the symbol that represents the atomic number?
Can be represented as the symbol Z
What is the symbol that represents the mass number?
Can be represented as the symbol A
What are the properties of isotopes?
They have similar chemical properties but different physical properties. Because they have the same number of electrons in their outershell.
Why do isotopes have different physical properties?
The only difference between isotopes is the number of neutrons.
Since they are neutral subatomic particles, they only add mass to the atom.
As a result of this, isotopes have different physical properties, such as small differences in their mass, density, melting point, and boiling point.
Define and give the role of the Mass Spectrometer
An instrument used to determine the relative isotopic mass and the relative abundance of each isotope.
Not only can it be used to find the masses of isotopes, it can also be used to detect illegal drugs, forensic science, space exploration, and carbon-14 dating.
Describe how the mass spectrometer works. Give the full description of the whole procedure.
- A sample is injected into the spectrometer, where it is heated and vaporised.
- The atoms or molecules are bombarded by high-energy electrons created by an electron gun.
- The high-energy electrons collide with the sample material and remove electrons, creating positive ions.
- The ions are then accelerated by attraction towards negatively charged plates.
- Many ions strike the plate and are discharged, but a few will pass through a gap in the plates into a curved section of the spectrometer known as the flight tube.
- The flight tube is encased in electromagnets, which create a strong electromagnetic field that deflects the path of the ions in a curve.
- The ions pass onto a charged detector plate, where every strike is recorded as a small current, which is then amplified.
- By varying the electric and magnet fields, all the charged particles can be detected by the detector, which gives information about the mass/charge ratio and abundance of each ion.
What is the formula to find the relative isotopic mass?
Relative isotopic mass = (abundance of atom 1 x atom 1 mass number) + (abundance of atom 2 x atom’s 2 mass number) DIVIDED ALL BY 100.
What is the mass/charge ratio?
- The mass/charge ratio (written as m/z) is a way to describe particles (usually ions) based on their mass and their charge.
- It is calculated by dividing the mass of the ion by its charge.
Mass/charge ratio = mass of the ion ( in atomic mass units, u) DIVIDED BY charge on the ion ( in multiples of the elementary charge)
For example:
If an ion has a mass of 12 u and a charge of +1, its m/z is 12/1=12.
If an ion has a mass of 16 u and a charge if +2, its m/z is 16/2 = 8
What does the m/z ratio mean?
- m/z is just the symbol for mass/charge ratio. It’s commonly used in mass spectrometry, where it helps identify ions.
- In the mass spectrometer, ions are separated based on their m/z, and a graph called a mass spectrum is produced. This graph shows the m/z values of the ions and their relative abundances.
What is a mass spectrum?
. What is a mass spectrum?
A mass spectrum is a type of graph produced in a mass spectrometer.
It shows:
1. The mass/charge ratio (m/z) of the ions detected.
2. The relative abundance of those ions (how much of each ion is present compared to the most common one).
Think of it as a “fingerprint” that helps identify substances based on their ions.
For example:
* On the x-axis, you’ll see m/z values (mass/charge ratio).
* On the y-axis, you’ll see relative abundance (how much of each ion there is).
What is a mass spectra of molecules?
The mass spectra of molecules are a collection of all the ions a molecule produces when it’s analysed in a mass spectrometer.
Here’s what happens:
1. Ionisation: The molecule is hit by high-energy particles and broken into ions.
2. Detection: The ions are separated by their m/z, and the mass spectrometer records them.
The resulting mass spectrum has peaks:
* A molecular ion peak (sometimes called M+): This shows the m/z of the original molecule after losing just one electron.
* Fragment peaks: These come from pieces of the molecule that broke apart during ionisation.
The mass spectra of molecules can help:
* Identify the molecular formula.
* Show how the molecule breaks apart (useful for organic chemistry!).
What does relative mean in general?
What does relative mean in general?
Relative means that something is compared to or measured against something else. It doesn’t stand alone—it only makes sense when there’s a comparison.
For example:
Saying “Alfred is tall” doesn’t tell us much unless we compare Alfred’s height to someone else or a standard. If we say, “Alfred is tall compared to his classmates,” we are using “relative.”
2. How does relative apply in science and chemistry?
In chemistry, relative often refers to measurements or quantities that are compared to a standard or reference.
Example 1: Relative Atomic Mass (Ar)
* The mass of an atom is compared to C12, which is assigned a value of exactly 12.
* So, the relative atomic mass of hydrogen is 1.008, meaning a hydrogen atom is about 1/12th the mass of a C12 atom.
Example 2: Relative Abundance
*In a mass spectrum, relative abundance shows how much of each ion there is compared to the ion with the highest abundance.
* For example:
If the most abundant ion is given a value of 100 and another ion has half as many particles, its relative abundance is 50.
Give some sentence examples of the word “relatively.”
Everyday Context:
The room felt relatively cold compared to the sunny weather outside.
This phone is relatively cheap compared to the latest flagship models.
The hike was relatively easy for someone who exercises regularly.
That car is relatively fast, but it’s not as fast as a sports car.
Scientific Context:
Helium is relatively lighter than oxygen, which is why balloons filled with helium float.
Copper is relatively a good conductor of electricity compared to rubber.
The experiment was relatively successful, but some errors occurred during data collection.
Sodium is relatively more reactive than magnesium in the periodic table.
Mathematical/Comparative Context:
John’s test score was relatively higher than the class average.
The moon is relatively closer to the Earth than the sun is.
What is the mass spectra of molecules about?
When a compound is analysed in a mass spectrometry, vaporised molecules are bombarded with a beam of high-speed electrons.
These knock off an electron from some of the molecule, creating molecular ions.
Molecule (electron bombardment) → molecule + e- molecular ion.
Fill in the gaps.
The ….. …. of the detected ions form a ….. … : a kind of …. fingerprint that can be idetified by a … using a …. database.
The relative abundances of the detected ions form a mass spectrum: a kind of molecular fingerprint that can be identified by a computer using a spectral database.
