Atomic Structure Flashcards
Which is the atomic number and what does it represent?
Smaller nos.
Protons
What is the mass of protons?
1
What is the mass of electrons?
Very small
What is the mass of neutrons?
1
What are isotopes?
Atoms of the same element which have different numbers if neutrons
How can elements and compounds be detected and identified?
By using instrumental methods. Instrumental methods are accurate, sensitive and rapid and are particularly useful when the amount of a sample is very small
What can chemical analysis be used to identify?
To identify additives in food. Artificial colours can be detected and identified by paper chromatography
Give an example of an instrumental method.
Gas chromatography linked to mass spectroscopy
What does gas chromatography allow and show?
It allows the separation of a mixture of compounds
The time taken for a substance to travel for a substance through the column can be used to help identify the substances
The output from the gas chromatography column, can be linked to a mass spectrometer, which can be used to identify the substances leaving the end of the column
How does gas chromatography (GC-MS) work?
Different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so that they become separated
The number of peaks on the output of the gas chromatograph shows the number of compounds present
The position of the peaks on the output indicates the retention time
What can a mass spectrum do?
It can identify substances very quickly and accurately and can detect very small quantities
It can also give the relative molecular mass of each of the substance separated in the column
Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of product. Why is this?
The reaction may not go to completion because it is reversible
Some of the product may be lost when it is separated fro the reaction mixture
Some of the reactants may react in ways different from the expected reaction
What are reversible reactions?
In some chemical reactions, the products of the reaction can react to produce the original reactants
Give an example of a reversible reaction.
Ammonium chloride (reversible sign) ammonia + hydrogen chloride
Which is the mass number and what does it represent?
Larger nos.
Protons and neutrons
