Inorganic chemistry

Fluorine is the most electronegative element on the Pauling scale due to its small atomic radius and high effective nuclear charge, which strongly attract bonding electrons. Option C is incorrect because chlorine, despite being in the same halogen group, has a larger atomic radius and more electron shielding, resulting in a lower electronegativity than fluorine.

Lanthanide contraction occurs because the 4f electrons have poor shielding ability, which fails to counteract the increasing nuclear charge across the series. This causes the outer electrons to be pulled more strongly, unlike in elements where well-shielding s or p electrons prevent such contraction.

Fluorine is the most electronegative element on the Pauling scale due to its small atomic radius and high effective nuclear charge, which strongly attract bonding electrons. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option C is incorrect because chlorine, despite being in the same halogen group, has a larger atomic radius and more electron shielding, resulting in a lower electronegativity than fluorine.
• !Lanthanide contraction occurs because the 4f electrons have poor shielding ability, which fails to counteract the increasing nuclear charge across the series.
• !Option B (+4) is incorrect because it represents the oxidation state of sulfur in sulfurous acid (H2SO3) rather than sulfuric acid.
• !Option A (He) is incorrect because helium's atomic number is 2, meaning its ground state configuration is 1s2, which does not contain any p orbitals.

Answer each from memory — you'll see instantly whether you're right and why.

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