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Some of the elements in the periodic table are metals: (a) The electronic configuration of a metal is 2.8.3 - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2019 - Paper 1
Question 4
Some of the elements in the periodic table are metals: (a) The electronic configuration of a metal is 2.8.3. Which row shows the group and period of the periodic t... show full transcript
Worked Solution & Example Answer:Some of the elements in the periodic table are metals: (a) The electronic configuration of a metal is 2.8.3 - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2019 - Paper 1
Step 1
Which row shows the group and period of the periodic table where this metal is found?
Answer
The electronic configuration of a metal is 2.8.3. This indicates that it has three electrons in its outermost shell. The group in the periodic table corresponds to the number of outer electrons. Therefore, the correct group is Group 3, and the period is Period 2, placing it in Row D of the given options.
Step 2
Describe what you would see when a small piece of rubidium is dropped on to water.
Answer
When a small piece of rubidium is dropped into water, it will react vigorously, producing hydrogen gas, which may ignite due to the heat of the reaction. You would observe the metal fizzling and moving around on the surface of the water, indicating a rapid reaction.
Step 3
Explain, in terms of their electronic configurations, why lithium is less reactive than potassium.
Answer
Lithium (2.1) has only one electron in its outer shell, while potassium (2.8.8.1) has one electron in its outermost shell too. However, potassium's outer electron is further away from the nucleus due to its larger atomic size, resulting in less effective nuclear attraction. Consequently, lithium, with its outer electron closer to the nucleus, experiences a stronger attraction, making it harder to lose that electron and thus less reactive overall.
Step 4
Calculate the relative atomic mass of lithium in this sample.
Answer
To calculate the relative atomic mass of lithium, we use the formula:
ext{Relative Atomic Mass} = rac{(7.59\% imes 6) + (92.41\% \times 7)}{100}
Calculating this gives: ext{Relative Atomic Mass} = rac{(7.59 \times 6) + (92.41 \times 7)}{100} \approx 6.92
Thus, the relative atomic mass of lithium in the sample is approximately 6.92, rounded to two decimal places.