Chemistry Foundations
4.3.4 - Common Small Molecules
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There are certain small molecules that you should be familiar with. They are shown below. For each one, you should learn the name, molecular formula and displayed formula.
Molecular formula:
H2O
Displayed formula:
Displayed formula of a water molecule.
Molecular formula:
H2O2
Displayed formula:
Displayed formula of a hydrogen peroxide molecule.
Molecular formula:
NH3
Displayed formula:
Displayed formula of an ammonia molecule.
Molecular formula:
CO2
Displayed formula:
Displayed formula of a carbon dioxide molecule.
Molecular formula:
CH4
Displayed formula:
Displayed formula of a methane molecule.
Molecular formula:
HCl
Displayed formula:
Displayed formula of hydrogen chloride.
Molecular formula:
O2
Displayed formula:
Displayed formula of oxygen molecule.
Molecular formula:
N2
Displayed formula:
Displayed formula of nitrogen.
Molecular formula:
H2
Displayed formula:
Displayed formula of hydrogen.
Note that in all of the molecules above, every atom has the number of bonds we would expect it to have based on the group number of its element. All of the carbon atoms have four bonds, the nitrogen atoms have three bonds, the oxygen atoms have two bonds, the hydrogen atoms have one bond, and the chlorine atoms have one bond.
Also, note that some of the molecules have the same name as the element they are made of. For example, an oxygen molecule is made of oxygen atoms. Usually if a molecule is made up of atoms that are all the same element, then the molecule is named after the element.
This means that there can be multiple different particles that have the same name. For example, an O atom is called 'oxygen' and an O2 molecule is also called 'oxygen'.
Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.
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What is the molecular formula of water?
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What is the molecular formula of hydrogen peroxide?
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What is the molecular formula of ammonia?
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What is the molecular formula of carbon dioxide?
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What is the molecular formula of methane?
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What is the molecular formula of hydrogen chloride?
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What is the molecular formula of oxygen?
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What is the molecular formula of nitrogen?
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What is the molecular formula of hydrogen?
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4.3.5 - Dot and Cross Diagrams of Molecules
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4.3.3 - Empirical Formulae
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