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Use of the Data Booklet is relevant to this question - CIE - A-Level Chemistry - Question 2 - 2010 - Paper 1
Question 2
Use of the Data Booklet is relevant to this question. The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in the Periodic Table. ... show full transcript
Worked Solution & Example Answer:Use of the Data Booklet is relevant to this question - CIE - A-Level Chemistry - Question 2 - 2010 - Paper 1
Step 1
What is the order of their first ionisation energies?
Answer
To determine the order of first ionisation energies of radon (Rn), francium (Fr), and radium (Ra), we need to consider the periodic trends in ionisation energy.
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Ionisation Energy Trend: Ionisation energy increases across a period and decreases down a group in the periodic table. Therefore, heavier elements generally have lower ionisation energies due to increased distance from the nucleus and electron shielding effects.
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Position of Elements:
- Francium (Fr) is in group 1 and is the heaviest alkali metal, thus it will have the lowest ionisation energy due to its size and shielding effects.
- Radium (Ra) is in group 2 and will have a higher ionisation energy than francium but lower than radon.
- Radon (Rn), being a noble gas, will have the highest ionisation energy among these elements because it has a full outer shell, making it more stable and requiring more energy to remove an electron.
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Order of Ionisation Energies: Given these considerations, the order from least to most endothermic (i.e., lowest to highest ionisation energy) is:
- Fr < Ra < Rn.
Thus, the correct answer is A: Fr, Ra, Rn.