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This question is about elements - AQA - GCSE Chemistry Combined Science - Question 7 - 2020 - Paper 1
Question 7
This question is about elements. Caesium is in Group 1 of the periodic table. 07.1 Explain what happens to caesium atoms and to oxygen atoms when caesium reacts wi... show full transcript
Worked Solution & Example Answer:This question is about elements - AQA - GCSE Chemistry Combined Science - Question 7 - 2020 - Paper 1
Step 1
07.1 Explain what happens to caesium atoms and to oxygen atoms when caesium reacts with oxygen to produce caesium oxide.
Answer
When caesium reacts with oxygen, it undergoes the following transformations:
- A caesium atom loses one electron to form a caesium ion, denoted as Cs⁺.
- An oxygen atom gains two electrons, forming an oxide ion (O²⁻).
- Thus, two caesium atoms combine with one oxygen atom to produce the compound, caesium oxide (Cs₂O).
Step 2
07.2 Explain why caesium is more reactive than sodium.
Answer
Caesium is more reactive than sodium due to several factors:
- Caesium has more energy levels than sodium, meaning its outer electron is located further from the nucleus.
- The outer electron in caesium experiences increased shielding from the positive charge of the nucleus.
- Consequently, the attraction between the nucleus and the outer electron is weaker, allowing the outer electron to be removed with less energy.
Step 3
07.3 Explain why the early periodic tables placed iodine (I) before tellurium (Te), but then Mendeleev placed tellurium before iodine.
Answer
In early periodic tables, elements were arranged based on atomic mass. Iodine, having a lower atomic mass than tellurium, was placed before it. However, Mendeleev modified the arrangement based on the elements’ chemical properties. He placed tellurium before iodine because they possess similar properties, which provided a more logical grouping in the periodic table.