Question

Elements A, B, and C with atomic numbers z, z + 1, z + 2 form positive ions having an equal number of electrons. Compare and contrast the sizes of the respective ions.

• A. $A^{+1}>B^{+2}>C^{+3}$
• B. $A^{+1}>C^{+3}>B^{+2}$
• C. $B^{+2}>A^{+1}>C^{+3}$
• D. $C^{+3}>A^{+1}>B^{+2}$

Answer 1

Answer: (A)

$A^{+1}>B^{+2}>C^{+3}$

For iso electronic species the element with more protons has smaller size. Thus $C^{+3}$ is smallest and $A^{+1}$ is largest. Thus correct order is

$A^{+1}>B^{+2}>C^{+3}$