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JEE Main 202116 MarchEvening Shift

Exam: JEE Main
Year: 2021
Date: 16 March
Shift: Evening Shift
Subject: Chemistry
Chapter: Classification of Elements and Periodicity in Properties

JEE Main 2021 · 16 March · Evening Shift · Chemistry · Classification of Elements and Periodicity in Properties

Identify the elements X and Y using the ionization energy values...

Identify the elements $X$ and $Y$ using the ionization energy values given below :

$\begin{cases}Ionizationenergy & ( kJ / mol ) \\ {1}^{st} & {2}^{nd} \\ X & 495 & 4563 \\ Y & 731 & 1450\end{cases}$

Options

A $X = Na; Y = Mg$
B $X = Mg; Y = F$
C $X = Mg; Y = Na$
D $X = F; Y = Mg$

Correct answer

A. $X = Na; Y = Mg$

Step-by-step solution

$Na \to \left[Ne\right]3{s}^{1}{IE}_{1}$ is very low but ${IE}_{2}$ is very high due to stable noble gas configuration of ${Na}^{+}$ .

$Mg \to \left[Ne\right]3{s}^{2}{IE}_{1}$ and ${IE}_{2} \to$ Low

${IE}_{3}$ is very high.

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