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1. (a) An atom of potassium has atomic number 19 and mass number 39 - Edexcel - GCSE Chemistry Combined Science - Question 1 - 2020 - Paper 1
Question 1
1. (a) An atom of potassium has atomic number 19 and mass number 39. (i) Give the electronic configuration of this potassium atom. (ii) This potassium atom forms th... show full transcript
Worked Solution & Example Answer:1. (a) An atom of potassium has atomic number 19 and mass number 39 - Edexcel - GCSE Chemistry Combined Science - Question 1 - 2020 - Paper 1
Step 1
Step 2
Which row shows the number of protons and the number of neutrons in this potassium ion, K<sup>-</sup>?
Answer
The correct answer is option B.
For the potassium ion K<sup>-</sup>, the number of protons is 19 (the atomic number of potassium) and the number of neutrons is 20. This gives the ion a total mass number of 39, consistent with the information provided.
Step 3
Explain, in terms of electrons, why potassium and caesium are in the same group.
Answer
Potassium (K) and caesium (Cs) are both in Group 1 of the periodic table, which means they have a single electron in their outermost shell. Since both elements have similar electronic configurations, with one valence electron in the outermost shell, they exhibit similar chemical properties and reactivity.
Step 4
Explain, in terms of these forces, why the boiling point of fluorine is low.
Answer
Fluorine molecules are held together by weak van der Waals forces (London dispersion forces). Due to the small size of fluorine molecules and the resulting weak intermolecular forces, less energy is required to break these forces. Therefore, fluorine has a low boiling point of -188°C.