JEE Main 2023 — Structure Of Atom Question with Solution
From: JEE Main 2023 (Online) 24th January Evening Shift
Question
The number of s-electrons present in an ion with 55 protons in its unipositive state is
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Correct answer
A10
Step-by-step explanation
The number of protons in an element determines its atomic number, which is the number of electrons in a neutral atom of the element. The unipositive state of an ion indicates that it has lost one electron. Therefore, the number of electrons in a unipositive ion is one less than the atomic number.
The element with 55 protons is cesium (Cs), which is in group 1 of the periodic table. Group 1 elements have one valence electron in the s sublevel of their outermost energy level.
In a neutral atom of cesium, there are 55 electrons, with the electron configuration [Xe] 6s1. When cesium loses one electron to form a unipositive ion (Cs+), the resulting ion has 54 electrons.
Out of this 54 electrons s subshell has 10 electrons in 1s2, 2s2, 3s2, 4s2, 5s2.
The element with 55 protons is cesium (Cs), which is in group 1 of the periodic table. Group 1 elements have one valence electron in the s sublevel of their outermost energy level.
In a neutral atom of cesium, there are 55 electrons, with the electron configuration [Xe] 6s1. When cesium loses one electron to form a unipositive ion (Cs+), the resulting ion has 54 electrons.
Out of this 54 electrons s subshell has 10 electrons in 1s2, 2s2, 3s2, 4s2, 5s2.
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This is a previous-year question from JEE Main 2023, covering the Structure Of Atom 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.