1. Tardigrade
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  4. If four elements with atomic numbers Z - 2, Z - 1, Z and Z + 1 are forming isoelectronic ions, the atomic number of the ion having largest size is

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Q. If four elements with atomic numbers $Z - 2, Z - 1, Z$ and $Z + 1$ are forming isoelectronic ions, the atomic number of the ion having largest size is

AP EAMCETAP EAMCET 2019

Solution:

$ \because\,\, 'Z'$ represents number of protons in a nucleus.

Therefore, for an isoelectronic species;

size of anion $>$ atom $>$ cation.

Means the species with more electrons w.r.t. protons in nucleus is of larger size [i.e. has smaller value of $Z$ ].

Thus, $Z-2$ has least number of protons, whereas $Z+l$ has maximum number of protons.

Hence, order of size for isoelectronic species will be

$Z - 2 > Z > Z + 1 $

Element with atomic number $Z-2$ is of largest size