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Statement I: In the graph of ionization energy (IE) versus atomic number Z (for Z = 1 to 60), the maxima correspond to noble gases and the minima correspond to alkali metals. Statement II: Across a period, the increasing nuclear charge generally outweighs the shielding effect, so the outer electrons are held more tightly.

1. Statement I is correct but Statement II is incorrect.
2. Both statements are correct.
3. Statement I is incorrect but Statement II is correct.
4. Both statements are incorrect.

Correct answer: Both statements are correct.

Solution

Statement I is correct: Noble gases have completely filled valence shells, making removal of an electron very difficult, hence they show maximum IE in each period. Alkali metals have a single valence electron that is poorly screened, making it easy to remove, so they show minimum IE. This is reflected in the IE vs Z graph from Z=1 to Z=60. Statement II is also correct: Across a period, Z increases while electrons are added to the same shell (poor shielding effect between same-shell electrons). The effective nuclear charge (Z_eff) increases, pulling the valence electrons closer and increasing IE. Both statements are correct and Statement II explains the trend in Statement I.

Related JEE Advanced Chemistry questions

• Which statement accurately describes the trend in chemical reactivity of alkali metals and halogens as their atomic number increases within the group?
• The process of converting O(g) into O²⁻(g) requires 603 kJ mol⁻¹ of energy. If the first electron affinity of O(g) is -141 kJ mol⁻¹, what is the value of the second electron affinity of oxygen?
• The sequence of increasing van der Waals radii for the elements O, N, Cl, F, and Ne is:
• Which of these sequences correctly represents the trend in electron affinity?
• Which of the following sequences of ionic sizes is accurate?
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