hi
are you sure the answer isn’t B)?
the radius trend for ions increases right to left, and top to bottom, BUT cations are smaller than anions for a same period
which leaves the order K⁺<Ar<Cl⁻
i found this similar question online for more explanation Arrange the following species in order of increasing size. Ar, K^ + , Cl^ - , S^2 - , Ca^2 +
oh yes! just relaized it should be B. thanks!!
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