C2.3 - Atomic Structure, Analysis and Quantitative Chemistry Flashcards
Which number is usually shown on the top of an element in the periodic table?
The Mass Number
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
Negligible
What is the mass number?
The total number of protons and neutrons in an atom.
What are isotopes?
Atoms of the same element that have different numbers of NEUTRONS.
What is the relative mass of an element compared to?
The C12 isotope
What is the Relative Formula Mass?
The sum of the relative atomic masses of the atoms shown in the formula.
How would you describe one mole of a substance?
The relative formula mass f a substance, in grams.
How can elements and compounds be detected and identified?
Using instrumental methods.
What are the advantages of instrumental methods?
They are accurate. sensitive and rapid and are useful when the amount of a sample is very small.
How can artificial colours in foods be detected?
Using paper chromatography.
What does gas chromatography allow?
The separation of a mixture of compounds.
How does gas chromatography work?
- Different substances, carried by a gas, travel through a column packed with solid material at different speeds, so that they become separated.
- The number of peaks on the output of a gas chromatograph shows the number of compounds present.
- The position of the peaks indicates retention time.
Why is a mass spectrometer linked to a gas chromatography column?
- It can be used to identify the substances leaving the end of the column.
- It can also give the relative molecular mass of each of the substances separated in the column, because the molecular mass is given by the ion peak.
