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1. Elements and compounds can exist as diatomic molecules - Scottish Highers Chemistry - Question 1 - 2022
Question 1
1. Elements and compounds can exist as diatomic molecules. (a) The seven elements that exist as diatomic molecules are shown in the periodic table below. (i) Expla... show full transcript
Worked Solution & Example Answer:1. Elements and compounds can exist as diatomic molecules - Scottish Highers Chemistry - Question 1 - 2022
Step 1
Explain why diatomic elements form non-polar molecules.
Answer
Diatomic elements form non-polar molecules because they consist of two identical atoms sharing electrons equally. The identical electronegativity values of the atoms mean that neither atom has a higher attraction for the bonding electrons, resulting in no charge separation across the molecule.
Step 2
Explain the decrease in covalent radius going from nitrogen to fluorine.
Answer
The covalent radius decreases from nitrogen to fluorine due to the increasing nuclear charge (the number of protons) without a corresponding increase in electron shell size. Fluorine has more protons, which pulls the electron cloud closer to the nucleus, reducing the covalent radius.
Step 3
Step 4
Explain why the first ionisation energy of the group 7 elements decreases going down the group.
Answer
The first ionisation energy of group 7 elements decreases down the group due to increased shielding from additional electron shells. This makes the outer electrons further from the nucleus and less strongly attracted, requiring less energy to remove them.
Step 5
State the name of the strongest type of intermolecular force found between hydrogen fluoride molecules and explain how this type of intermolecular force arises.
Answer
The strongest type of intermolecular force in hydrogen fluoride is hydrogen bonding. It arises from the attraction between the partially positive hydrogen atom covalently bonded to a strongly electronegative atom (fluorine) and the lone pair of electrons on the fluorine atom of a neighboring HF molecule.
Step 6
Explain fully why the boiling point increases from hydrogen chloride to hydrogen iodide.
Answer
The boiling point increases from hydrogen chloride (HCl) to hydrogen iodide (HI) due to the increasing size and polarizability of the iodine atom compared to chlorine. Hydrogen iodide experiences stronger London dispersion forces due to the larger number of electrons, which outweighs the weaker hydrogen bonding present in HCl, thereby resulting in a higher boiling point.