Refer to page 79 of the Formulae and Tables booklet when answering this question - Leaving Cert Chemistry - Question 9 - 2020
Question 9
Refer to page 79 of the Formulae and Tables booklet when answering this question.
a) (i) What is the number of electrons in each of the main energy levels (shells)
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Worked Solution & Example Answer:Refer to page 79 of the Formulae and Tables booklet when answering this question - Leaving Cert Chemistry - Question 9 - 2020
Step 1
What is the number of electrons in each of the main energy levels (shells) in an oxygen atom?
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Answer
An oxygen atom has a total of 8 electrons. The distribution of these electrons in the energy levels is as follows:
2 electrons in the first shell
6 electrons in the outer (valence) shell.
Step 2
What is the number of electrons in each of the main energy levels (shells) in a magnesium atom?
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Answer
A magnesium atom has a total of 12 electrons. The distribution is:
2 electrons in the first shell
8 electrons in the outer (valence) shell.
Step 3
Define oxidation in terms of electron transfer.
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Answer
Oxidation is defined as the loss of electrons during a chemical reaction. It involves an increase in the oxidation state of a substance.
Step 4
Define reduction in terms of electron transfer.
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Reduction is defined as the gain of electrons during a chemical reaction. It results in a decrease in the oxidation state of a substance.
Step 5
Which element is reduced?
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Answer
In the reaction 2Mg + O2 → 2MgO, oxygen (O) is the element that is reduced, as it gains electrons.
Step 6
Which substance is the reducing agent?
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Answer
In this reaction, magnesium (Mg) acts as the reducing agent, as it donates electrons to oxygen.
Step 7
Give two characteristic properties of ionic substances.
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Answer
Ionic substances generally exhibit the following characteristics:
They have high melting and boiling points due to strong ionic bonds.
They conduct electricity when molten or dissolved in water due to the mobility of ions.
Step 8
What does this result tell you about how easily magnesium metal is oxidised compared to copper metal?
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Answer
The fact that magnesium displaces copper from its solution indicates that magnesium is more easily oxidised than copper. This suggests that magnesium has a higher tendency to lose electrons compared to copper.
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