JEE Main 2023 — S Block Elements Question with Solution
From: JEE Main 2023 (Online) 12th April Morning Shift
Question
The density of alkali metals is in the order :
Choose an option
Show full solutionCorrect option: B
Step-by-step explanation
Alkali metals are part of Group 1 on the periodic table and include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). As you move down the group, the atomic radius increases due to the addition of energy levels (shells). While you might think that the increased atomic mass would correspond to an increase in density, the increase in atomic radius generally outpaces the increase in atomic mass, leading to a decrease in density.
The densities (at room temperature) of the mentioned alkali metals are :
- Sodium (Na) : 0.97 g/cm³
- Potassium (K) : 0.86 g/cm³
- Rubidium (Rb) : 1.53 g/cm³
- Cesium (Cs) : 1.93 g/cm³
So, the order of densities is : K < Na < Rb < Cs
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This is a previous-year question from JEE Main 2023, covering the S Block Elements chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.