Question

Based on their positions in the periodic table, list the following ions in order of increasing radius: K+, Ca²+, Al³+, Si⁴+.

a) S^i4+, Al³+, Ca²+, K+
b) K+, Ca²+, Al³+, Si⁴+
c) Si⁴+, Al³+, K+, Ca²+
d) Ca²+, K+, Al³+, Si⁴+

Answer 1

The order of increasing ionic radius for K+, Ca2+, Al3+, Si4+ is: Si4+ < Al3+ < Ca2+ < K+, with nuclear charge decreasing as radius increases. The correct option is A.

Step-by-step explanation:

The order of increasing ionic radius in the periodic table is influenced by both the nuclear charge and the number of electron shells. For ions with the same electronic configuration, the nuclear charge dictates that the more positively charged ions (those with more protons) will attract the electrons more strongly, leading to a smaller radius.

Therefore, when comparing K+, Ca2+, Al3+, and Si4+ ions, which are isoelectronic, the ionic radius increases as the nuclear charge decreases.

Following this rule, the ions should be arranged as follows: Si4+ < Al3+ < Ca2+ < K+. This is because Si4+ has a higher nuclear charge and fewer protons than the other ions, and K+ has the lowest nuclear charge among them.