JEE Advanced 2020 · Paper 2 · Chemistry Q1

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ChemistryInteger+3 / -1Question 19 of 54

The 1st, 2nd, and the 3rd ionization enthalpies, $I_1$ , $I_2$ , and $I_3$ , of four atoms with atomic numbers $n$ , $n+1$ , $n+2$ , and $n+3$ , where $n < 10$ , are tabulated below. What is the value of $n$ ?

Ionization enthalpies (kJ/mol) of four consecutive elements.

Your answer

Answer and worked solution

Official answer: 9

Read the table.

$n+2$ has a very low $I_1$ (496) and a huge jump to $I_2$ : an alkali metal.
$n+3$ has a low $I_1$ and $I_2$ and a huge jump to $I_3$ : an alkaline earth metal.

With $n<10$ , $n+2$ is Na (11) and $n+3$ is Mg (12). Then $n$ is F (I₁ = 1681) and $n+1$ is Ne (I₁ = 2081), which both fit.

Answer: 9

Topics:Ionisation enthalpy

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JEE Advanced 2020 · Paper 2, Chemistry question 1