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This question is about the properties of elements in Groups 1, 7 and 0 - OCR Gateway - GCSE Chemistry - Question 20 - 2019 - Paper 4
Question 20
This question is about the properties of elements in Groups 1, 7 and 0. (a) Lithium, sodium and potassium are all Group 1 elements. A teacher adds a small piece of... show full transcript
Worked Solution & Example Answer:This question is about the properties of elements in Groups 1, 7 and 0 - OCR Gateway - GCSE Chemistry - Question 20 - 2019 - Paper 4
Step 1
Describe what else you would observe.
Answer
As potassium is added to water, you would observe the potassium piece bobbing on the surface due to the gas produced, which is hydrogen. There would be a noticeable fizzing and effervescence as hydrogen gas escapes. Additionally, the water may appear to become warmer as the reaction is exothermic.
Step 2
Explain this trend in reactivity.
Answer
The reactivity of Group 1 elements increases down the group due to their electronic configurations. Lithium has the configuration 1s² 2s¹, sodium has 1s² 2s² 2p⁶ 3s¹, and potassium has 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. As we move down the group, the outer electron is further from the nucleus due to increasing atomic radius, which results in a weaker electrostatic attraction between the positively charged nucleus and the outer electron. Consequently, it becomes easier for potassium to lose its outer electron compared to lithium, leading to increased reactivity.
Step 3
Step 4
Step 5
Explain why, in terms of their electronic configurations.
Answer
The elements in Group 0 (noble gases) are unreactive because they have a full outer shell of electrons, which makes them stable. This electronic configuration means they do not tend to gain, lose, or share electrons with other elements, resulting in low reactivity.